FINANCE Ministers from some of the world’s leading economies say that a UK exit from the European Union would provoke a global economic shock.

Brexit was flagged up in negative terms in a communique after a meeting of G20 finance ministers in Shanghai, China - a development welcomed by Chancellor George Osborne.

The warning came as Scotland Stronger In Europe – the group working for the UK to remain an EU member – stepped up its campaigning this weekend.

The UK will have a referendum in June on EU membership after the Prime Minister unveiled a package of reforms agreed with fellow member states earlier this month.

However, although the Remain option will be supported by the Tory, Labour, Liberal Democrat and SNP leaders, Cameron is facing opposition from key members of his own party.

Justice Secretary Michael Gove and London Mayor Boris Johnson irritated Cameron by backing Brexit.

Speaking in Shanghai yesterday, Osborne, said the intervention of his G20 finance counterparts was significant.

"Finance leaders and central bank governors of the world's biggest economies have raised serious concerns about the risks posed by a UK exit from the EU.

"They have concluded unanimously today that what they call the shock of a potential UK vote to leave is among the biggest economic dangers this year.

"If that's their assessment of the impact on the world economy, imagine what it would do to the UK."

However, UKIP leader Nigel Farage, a key Brexit figure, hit back by saying the G20 announcement was "no surprise" and was "mates helping each other out".

Osborne also took a swipe at Johnson, who is considered his main rival for the Tory leadership when Cameron stands down.

The Mayor faced accusations of "flip-flopping" after he ruled out the possibility of a vote to leave on June 23 leading to a better offer from Brussels and a second referendum.

Osborne said: "This isn't some amusing adventure into the unknown. A British exit would hurt people's jobs, livelihoods and living standards - it's deadly serious.

"It's my responsibility as Chancellor to make it clear to people what the economic risks are - and that we are stronger, safer and better off remaining in a reformed EU."

One of the UK's leading scientists has also warned against leaving the EU, saying the country "cannot afford to be an island" in research.

Sir Paul Nurse - the Nobel Prize-winning director of the Francis Crick Institute - said Britain is "too small to be effective" outside the "powerhouse" of the 28-nation block.

The former president of the Royal Society also accused "naive" pro-Brexit campaigners such as Gove of "intellectual laziness".

The Justice Secretary had said that the EU clinical trials directive had "slowed down the creation of new drugs to cure terrible diseases".

Sir Paul told BBC Radio 4's Today programme: "He is wrong about this. We have plenty of bureaucracy in the UK about this, I fight it myself.

"If we are to really make science work, we have to be part of the European Union, we have to influence the agenda, we have to make the regulations work.

"We are too small to be effective. We are an island. We cannot afford to be an island in science. If we are part of the European Union we are part of a powerhouse that can produce the data.

"We have to work with them and we will have no impact if we are outside. It will make it worse. It is naive, this argument."

A rival anti-EU group has been set up under the Scientists for Britain banner.

Its spokesman, Professor Angus Dalgleish, told the BBC: "We are standing up against what is a very large body of people who feel that if we leave the EU it will be a disaster for funding and collaboration - and we completely refute that."

Meanwhile, Scotland Stronger In Europe rolled out its pro-EU message in Edinburgh, Glasgow, Dundee, Aberdeen and Banchory yesterday.

The campaign, which has brought together figures in the SNP and Labour, claimed that 336,000 Scottish jobs are linked to the EU.

Senior campaign spokesperson John Edward said: "The polls show Stronger In with a big lead in Scotland but we are not complacent, which is why we are working hard.

"Our research shows that people want the facts on the benefits of being in the EU, and that the more informed they feel themselves to be, the more likely they are to vote to stay in Europe.”