Brexit ‘bad boy’ Arron Banks has sparked fury after tweeting a sick 'joke' about Greta Thunberg drowning during her transatlantic yacht voyage.

The Swedish schoolgirl, 16, is making the trip across the Atlantic on a high-tech racing yacht, the Malizia II, so she can attend high-profile climate events in the US and Chile while keeping her carbon emissions low.

Commenting on a post in which Thunberg announced she was off the English coast, Mr Banks wrote: 'Freak yachting accidents do happen in August.'

Brexit donor Arron Banks has been slammed for a sick 'joke' about climate change campaigner Greta Thunberg drowning in a yachting accident 

Replying to one user saying the tweet had 'shown his true colours', he wrote: 'It was a joke… you lefties have no sense of humour'

Radio host Julia Hartley-Brewer also criticised Mr Banks for his comment, writing, 'She's a child, Arron. FFS' 

The Swedish schoolgirl, 16, is making the trip across the Atlantic on a high-tech racing yacht, the Malizia II, so she can attend high-profile climate events in the US and Chile while keeping her carbon emissions low

The 60-ft boat, Malizia II is capable of travelling at speeds of up to 43mph - powered by the wind - although it will be sailing mostly into the wind on its way across the Atlantic 

The message prompted a storm of criticism, including from arch Thunberg critics like radio host Julia Hartley-Brewer, who tweeted: 'She's a child, Arron. FFS.'

Mr Banks responded: 'Quite and one being used. Obviously I don’t hope she encounters a freak yachting accident! I just enjoy watching the ludicrous tweeter mob following the next outrage.’

Replying to another user saying the tweet had 'shown his true colours', he wrote: 'It was a joke… you lefties have no sense of humour.'

Other Twitter users also slammed Mr Banks in replies to his tweet, with one writing: 'Beyond despicable. This utterly vile. How could anyone imagine being on the same side as you was a good place to be.'

Svenja O'Donnell tweeted: 'It's appalling that you wish harm upon a child, whether you agree with her or not.'

'Sammi' said: 'In what world did you think it was a good idea to send that tweet out to the world? Just plain nasty.'

Another user, James Phillips, called Mr Banks a 'despicable little man'.

Even critics of Ms Thunberg criticised him, with one user writing: 'Although I think her journey via yacht is ridiculous, this tweet is in poor taste, Arron.'

Another Twitter user, Madeline Grand, wrote: 'Good grief this is appalling.'

And fellow Banks critic Sarah Rosemary said: 'I appreciate you do this for effect, but you're wishing death on a child now?' 

Originally a modest Tory donor, in 2014 Mr Banks defected to Ukip in anger at then-PM David Cameron's stance on Europe. He is pictured in a file photo 

Other Twitter users also slammedMr Banks in replies to his tweet, with one writing: 'Beyond despicable. This utterly vile'

Ms Thunberg decided to take a wind-powered racing yacht across the Atlantic to attend UN summits on tackling global warming, after deciding flying or taking a cruise ship would emit too much carbon.

The teenager, whose 'school strikes' have inspired a global protest movement by young people demanding urgent action on climate change, said she would not bother trying to meet Trump when she arrives in the US because he has already ignored the views of climate scientists.

'I don't see that if anyone else has succeeded... I am not that special,' she said.

She is also planning to visit Canada and Mexico before travelling to this year's UN climate conference, which is taking place in Santiago, Chile, in December, making her journeys by train and bus.

Meanwhile, Mr Banks was recently the subject of allegations that he may have been involved in smuggling diamonds out of South Africa, it has been alleged.

Britain's National Crime Agency has been passed claims that Mr Banks, who owns diamond mines in South Africa, tried to get hold of black-market diamonds from Zimbabwe.

Who is Arron Banks - the man who 'bought Brexit'? 

Mr Banks, 53, made his fortune from the Bristol-based insurance broker Brightside which he founded

Arron Banks has been dubbed ‘the man who bought Brexit’ for the way he bankrolled Nigel Farage’s campaign to leave the EU.

The multi-millionaire has donated millions to Ukip and in 2016 he backed Mr Farage’s Leave.EU group.

He was pictured alongside Donald Trump when the President met Nigel Farage in New York just days after his shock US election victory.

But now he is facing calls to explain a series of meetings with Russian embassy officials.

Mr Banks, 53, made his fortune from the Bristol-based insurance broker Brightside which he founded. He then went on to found another firm, GoSkippy, and is now said to be worth £100million.

He is married to Russian Ekaterina Paderina and has five children.

Originally a modest Tory donor, in 2014 he defected to Ukip in desperation at David Cameron’s stance on Europe.

William Hague made the mistake of describing Mr Banks as ‘somebody we haven't heard of’ following his defection – prompting him to up his donation to £1million.

He said: ‘I woke up this morning intending to give £100,000 to UKIP – then I heard Mr Hague's comment about me being a Mr Nobody. So in light of that I have decided to give £1million.’ 

Teenage climate change activist Ms Thunberg departed Plymouth on her trip to New York to attend a United Nations climate change conference

Ms Thunberg waits on a dinghy to board the Malizia II boat in Plymouth

Ms Thunberg and the crew's Pierre Casiraghi and Boris Herrmann wave from the Malizia II boat, as she starts her trans-Atlantic boat trip to New York

The activist waves to well-wishers while leaving Plymouth on Thursday. Ms Thunberg is making her way from Plymouth to New York aboard the Malizia II to attend the climate change conference in September

It is alleged that he was trying to supplement his South African diamond exports with the illegal supply from Zimbabwe, pretending they were all from his mines, according to The Sunday Times.

Mr Banks has denied ever being involved in diamond smuggling in South Africa or any other African country, and insisted he had not been questioned by the NCA over the allegations or told that the agency was looking into the issue.

The businessman is already under investigation by the NCA over his donation to Leave.EU three years ago.

Ms Thunberg decided to take a wind-powered racing yacht across the Atlantic to attend UN summits on tackling global warming

The Electoral Commission had referred the case after investigating whether Mr Banks was the 'true source' of the funding.

He made his fortune from the Bristol-based insurance broker Brightside which he founded.

Mr Banks, who is married to Russian Ekaterina Paderina and has five children, then went on to found another firm, GoSkippy. It is now said to be worth £100million.

Originally a modest Tory donor, in 2014 he defected to Ukip in anger at then-PM David Cameron's stance on Europe.

He was pictured alongside Donald Trump when the President met Nigel Farage in New York just days after his shock US election victory.

Last year Mr Banks claimed he had rejoined the Conservative party along with his associate Andy Wigmore but the Tories said their applications had been rejected.

In May 2018 Leave.EU was handed a fine of £70,000 for breaching finance rules in the 2016 referendum.

After failing to become the lead campaign group for the pro-Brexit movement, it had a spending limit of £700,000 but the Electoral Commission found it exceeded that cap.

Earlier this year the European Parliament said it would investigate claims that Mr Banks had donated £450,000 to Mr Farage after the referendum.

Greta Thunberg refuses to travel to the US by cruise ship or plane: Here's why

The climate change activist has ruled out flying on a plane for the trip because on average, a plane produces a little over 53 pounds of carbon dioxide per air mile.

For example, non-stop flights from London to New York City take between 8 to 10 hours based on the airline. 

There are 3,470 miles between London and the Big Apple. When that number is multiplied by 53 it equates to about 183,910 pounds of emissions per flight between the two cities.

Ms Thunberg waved from the bow of the zero emissions racing yacht as it left Plymouth

Ms Thunberg also refuses to travel aboard a cruise ship because they're notoriously big polluters.

Most cruises travel from the East Coast of the US to the UK – usually England. By sea, it will take six or seven days in transit, and sometimes longer.

A single large cruise ship can emit over five tons of oxides of nitrogen.

Ms Thunberg has opted to take on the Atlantic on a high-tech yacht, known as the Malizia II.

The journey from the UK to New York will take approximately two weeks on the Malizia II.

The boat is fitted with solar panels and underwater turbines that allow it to generate zero-carbon electricity on board

It will be captained by yachtsman Boris Herrmann.