Arron Banks has been criticised after he sent a “vile” tweet about teenage climate activist Greta Thunberg as she set sail across the Atlantic to attend UN summits on global warming.

The billionaire Leave.EU founder warned the 16-year-old that “freak yachting accidents do happen in August” in response to a tweet by Green Party MP Caroline Lucas who praised Ms Thunberg for her “zero-carbon trip”.

Mr Banks later tweeted that his comment was a “joke” after it sparked outrage among MPs, celebrities and academics.

In reply to the Brexit backer’s response to her tweet, Ms Lucas wrote: “Arron Banks’ vile tweet about @GretaThunberg makes me sick to the stomach. I have made a formal complaint to Twitter.”

Labour MP David Lammy described the post as "nasty, wicked" and "evil".

Greta Thunberg inspires climate activists everywhere: In pictures Show all 12 1 /12 Greta Thunberg inspires climate activists everywhere: In pictures Greta Thunberg inspires climate activists everywhere: In pictures In the protest that started a movement, Greta skips school to sit outside of the Swedish parliament in Stockholm in order to raise awareness of climate change on 28 August 2018 Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the World Economic Forum in Davos on 25 January AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta stages a protest at the World Economic Forum in Davos on 25 January Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the House of Commons in London on 23 April PA Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses to the occupation at Marble Arch in London on 21 April AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta meets the pope on a visit to Rome Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta speaks at the senate in Rome on 18 April Reuters Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses a debate of the EU Environment, Public Health and Food Safety committee at the European Parliament in Strasbourg on 16 April AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta receives the Special Climate Protection Award at the German Film and Television awards in Berlin on 30 March AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta attends a children's climate protest in Berlin on 29 March AFP/Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta addresses a children's climate protest on 1 March in Hamburg Getty Greta Thunberg inspires climate activists everywhere: In pictures Greta attends a meeting for the Civil Society For rEUnaissance at the EU Charlemagne Building in Brussels on 21 February AFP/Getty

"And terribly sad this man has bankrolled the peril facing our country," he added.

Sherlock actor Amanda Abbington tweeted: “You’re wishing a potentially fatal accident onto a sixteen year old girl, why..?”

Earlier, she wrote: “If you are a grown up, fully-fledged adult and you are mocking this young girl for trying to save the planet then I genuinely feel sorry for you. I also think you are incredibly cruel, vicious and ignorant.”

Femi Oluwole, the co-founder of pro-EU campaign group Our Future Our Choice, tweeted: “Just the man who's been bankrolling Brexit and Nigel Farage since the start threatening to kill an autistic child...”

Professor Tanja Bueltmann, founder of campaign group EU Citizens’ Champion, wrote: “I didn’t think Arron Banks could possibly sink any lower. He did.”

Radio presenter Julia Hartley-Brewer was also among those criticising Mr Banks, and tweeted: “She's a child, Arron. FFS.”

However, she went on to criticise the teenage climate activist herself. “Hi Greta, I’ve just booked some long haul flights for my family to enjoy some winter sun on the beach this Christmas. Level of guilt being felt: 0%," she wrote.

Ms Hartley-Brewer added: "St Greta is a political campaigner to be debated or she is a child to be ignored. Pick one."

Mr Banks later defended his post and, in response to a tweet which highlighted the fact Greta was a child, he said: "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 ..."

Later, replying to a tweet accusing him of showing “his true colours”, he wrote: “It was a joke… you lefties have no sense of humour”.

Ms Thunberg is embarking on a two-week voyage across the Atlantic on a carbon-neutral racing yacht to attend UN climate summits in New York and Chile as she refuses to fly on planes.

The founder of the “School Strike 4 Climate" movement said she is taking a year off school to raise awareness of the climate crisis and pressure world leaders to step up efforts to cut greenhouse emissions.

Ms Thunberg told the BBC that travelling by boat sends a signal that "the climate change crisis is a real thing".

The Malizia II yacht, which she is sailing on, is fitted with solar panels and underwater turbines to generate zero-carbon electricity on board.