Over half a million public sector jobs would be at risk by more austerity if Britain votes to pull out of the European Union, Labour politicians and union leaders will warn on Tuesday.

In a statement to The Independent and signed by over thirty Labour figures including Ed Balls, Andy Burnham and Harriet Harman say that Brexit would lead to a £40 billion black hole in the British economy that would have to be filled by tax rises or public sector cuts.

They suggest that given that the Conservative Government has chosen to cut the current deficit primarily by public sector austerity this is likely to be repeated if Britain were to vote to leave.

The statement comes as another poll suggests support for the Leave campaign is solidifying. An ICM poll for the Guardian found Leave now has a 53 to 47 per cent advantage once “don’t knows” are excluded.

Prof John Curtice of Strathclyde University, who analyses all the available referendum polling data noted that, after the new ICM data, the running average “poll of polls” would stand at 52 per cent for leave and 48 per cent for remain, the first time leave has been in such a position.

The Leave lead puts pressure not just on David Cameron but also on Labour who have been accused on running a lacklustre campaign – with many of the party’s traditional supporters likely to back Brexit.

The statement on job losses is intended to appeal to those worried about what might happen if a Conservative Government was responsible for dealing with the aftermath of Brexit.

Those behind the statement point out that between 2009 and 2015, the public sector workforce fell by 969,000. Over this period the budget deficit was reduced from £103.2bn to £40.5bn.

In the case of Brexit, they say, public sector tax receipts have been predicted by the Institute of Fiscal Studies to fall by another £40 billion.

They suggest this could mean the number of public sector employees would have to fall by a further 525,000 in order to balance the books.

“Independent economic experts agree that leaving Europe could hit our economy, including the Governor of the Bank of England who warned we could go into recession,” they write.

“Britain’s vital public services like the NHS rely on a strong economy and continued investment. But if we leave the shock to our economy could see a £40bn black hole in our public finances, that would hobble our public services and affect workers on the front line. Leaving Europe is a leap into the dark and is a risk for Britain’s public services that we cannot afford to take.”

Meanwhile Jeremy Corbyn will today return to the campaign trail with a major speech on Europe following growing grumbling with his party that he is not be active enough battling for a remain vote.

At an event at the TUC Congress House Labour’s Shadow Cabinet will come together to make a joint call to Labour voters ahead of the EU referendum. The General Secretaries of some of Britain’s major trade unions will also be present to show their support.

What has the EU ever done for us? Show all 7 1 /7 What has the EU ever done for us? What has the EU ever done for us? 1. It gives you freedom to live, work and retire anywhere in Europe As a member of the EU, UK citizens benefit from freedom of movement across the continent. Considered one of the so-called four pillars of the European Union, this freedom allows all EU citizens to live, work and travel in other member states. What has the EU ever done for us? 2. It sustains millions of jobs A report by the Centre for Economics and Business Research, released in October 2015, suggested 3.1 million British jobs were linked to the UK’s exports to the EU. What has the EU ever done for us? 3. Your holiday is much easier - and safer Freedom to travel is one of the most exercised benefits of EU membership, with Britons having made 31 million visits to the EU in 2014 alone. But a lot of the benefits of being an EU citizen are either taken for granted or go unnoticed. What has the EU ever done for us? 4. It means you're less likely to get ripped off Consumer protection is a key benefit of the EU’s single market, and ensures members of the British public receive equal consumer rights when shopping anywhere in Europe. What has the EU ever done for us? 5. It offers greater protection from terrorists, paedophiles, people traffickers and cyber-crime Another example of a lesser-known advantage of EU membership is the benefit of cross-country coordination and cooperation in the fight against crime. What has the EU ever done for us? 6. Our businesses depend on it According to 71% of all members of the Confederation of British Influence (CBI), and 67 per cent of small and medium-sized enterprises (SMEs), the EU has had an overall positive impact on their business. What has the EU ever done for us? 7. We have greater influence Robin Niblett, Director of think-tank Chatham House, stated in a report published last year: “For a mid-sized country like the UK, which will never again be economically dominant either globally or regionally, and whose diplomatic and military resources are declining in relative terms, being a major player in a strong regional institution can offer a critical lever for international influence.

Speaking at the event Mr Corbyn MP is expected to say they have just nine days to save Britain’s place in the EU.

“Today sees my shadow cabinet and the trade union movement join together, in the interests of the people of this country, to make Labour’s case to remain in the European Union and bring reform to strengthen workers’ rights,” he will say.

“That’s why today I am issuing a call to the whole Labour movement, to persuade people to back Remain to protect jobs and rights at work.

“We have just nine days to go to convince Labour supporters to vote Remain.”

Alan Johnson MP, Chair of Labour IN, said the fears over public sector job cuts did not amount to more project fear.

“This is an unprecedented warning from people across the Labour movement who believe in protecting our vital public services,” he said.

“It underlines the catastrophic impact that leaving the EU could have on those employed in our public sector and those who rely on it to get by.