Jeremy Corbyn would return Britain to a tax-and-spend economy costing £55billion a year, a Labour analysis of his policies has found.

The veteran Marxist’s hard-Left agenda of opposing welfare cuts would mean higher borrowing or extra pain for taxpayers, it claims.

The true figure is likely to be even higher as the calculation does not include key commitments like renationalising the railways and public utilities, which would cost billions in compensation to private industry.

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Jeremy Corbyn, pictured today in Leeds, would return Britain to a tax-and-spend economy costing £55billion a year, a Labour analysis of his policies has found

The analysis of his economic policies – dubbed ‘Corbynomics’ – were carried out by a Labour insider who is not a supporter of the North London MP.

It shows the Labour leadership frontrunner has already proposed £14billion of tax rises to pay for policies including free universal childcare and further education.

It suggests a further £40billion would need to be raised through increasing debt to meet the rest of his spending pledges like reversing welfare cuts and abolishing tuition fees.

The end result would mean little progress towards cutting the UK’s huge deficit.

The source said: ‘It was bad enough that the two Eds [Balls and Miliband] couldn’t admit our mistakes.

'If Corbyn takes over with plans like these we can kiss goodbye to power for a generation. People in dire straits need us to be electable.’

The analysis comes amid a backlash over what shadow chancellor Chris Leslie yesterday called ‘Corbynomics’.

He said the socialist’s ‘starry-eyed hard-Left’ economic strategy would push up inflation and interest rates, undermine support for public services and deliver a decade or more of Conservative rule.

Mr Leslie, who is backing Yvette Cooper in the leadership race, told The Independent: ‘You have got to have a credible Labour prime minister who understands this. Otherwise you have a decade or more of Tory rule.’ He confirmed that ‘on principle’ he did not think he would be able to serve in a shadow cabinet under the left-winger.

Mr Corbyn was mobbed by supporters at a leadership campaign rally at Camden Town Hall last night

Richard Murphy, the tax expert recruited by Mr Corbyn to draft his economic policy, said: ‘Leslie has got this completely wrong.’

He told Radio 4’s World At One programme there would be a ‘small rise in inflation’ but claimed it would ‘be used responsibly’.

Mr Corbyn’s £55billion of extra spending includes £12billion to scrap the Tories’ entire welfare proposals – such as the two-child limit for tax credits.

Opposing further public spending cuts would cost £20billion, while abolishing student fees would cost £7billion. Free universal childcare would set the Treasury back another £7billion. Mr Corbyn has also made a total of £14billion of tax rise proposals, including raising £1billion by not cutting inheritance tax and slapping 7 per cent on national insurance for earnings of £50,000 or more.

The socialist has also hinted at reinstating the 50p top rate of income tax, and a ‘windfall’ tax on vast wealth.

Panicked Labour MPs have rounded on leadership contender Jeremy Corbyn, warning his hard-left economic policies would be a 'recipe for disaster'

The rally, which was also attended by Ken Livingstone, Owen Jones and Mark Serwotka, saw queues of people desperate to listen to what Mr Corbyn had to say, forcing him to stand on a fire engine to address the crowd

Yesterday Liz Kendall – seen as the most Blairite of the four leadership contenders – said Mr Corbyn’s agenda was ‘neither realistic nor electable’. But former Tory Chancellor Ken Clarke called the Marxist MP a ‘nice guy’ who could win the next election if there was another recession.

As polls continue to put Mr Corbyn ahead in the leadership race, 600 supporters packed into a campaign rally in Camden, North London, last night – with another 500 forced to wait outside.

Mr Corbyn told the crowd that said Labour had been wrong to accept Conservative arguments on the economy and blamed it for May's devastating general election defeat.

He said: 'It's an incredible evening when we have had to have overflow meetings in the council chamber, downstairs and on top of the FBU fire engine outside.

'After September 12, whatever the result, don't go away and say that was a good summer 2015... stay together to defend what we have got but above all, stay together to bring about a country that doesn't thrive on inequality and injustice and poverty.

'A country that instead genuinely does care for all, that does provide public services that are good for all, does expand our economy, does take back into public ownership crucial monopolies like railways, Royal Mail and so many others, that doesn't give up the fruits of what we are trying to do and doesn't allow this Tory Government to take away our workers' rights and our trade union rights.'

Mr Corbyn stands on a fire engine to address hundreds of the overflow crowd outside Camden Town Hall

In a 30-minute speech made without notes, Mr Corbyn also claimed it was the Tories who looked like a throwback to the 1980s as he rejected claims he would take Labour back to the days of successive defeats to Conservative majority government.

And he attacked 'disgusting language' used about the migrant crisis in Calais.

Mr Corbyn also said that a 'number of people are taking notice' of the Labour campaign, which continues to challenge austerity.

He added to Channel 4 News: 'A number of people are taking notice of our campaign where we are challenging the agenda of austerity, austerity which has led to greater inequality in our society, greater poverty in our society and now the budget and welfare reform bill which will deepen that.