It will cost £100bn to fulfil Jeremy Corbyn’s aim of scrapping current student debt, Labour’s Shadow Education Secretary has admitted.

Angela Rayner said the policy remained an “ambition” because Labour does not know how it could be funded.

Asked on the BBC’s Andrew Marr Show how much the plan would cost, she said: “It’s a huge amount – it’s £100bn, which they estimate currently. It’s a huge amount of money. But we also know that a third of that is never repaid.

“But we’ve got to start dealing with this debt crisis that we’re foisting on our young people. They’re leaving university with £57,000 worth of debt. It’s completely unsustainable and we’ve got to start tackling that.

Ms Rayner, an ally of Mr Corbyn, called on ministers to reduce the student debt burden by reversing the abolition of maintenance grants, reducing the interest rate on debt and raising the threshold at which repayments must be made.

Last month, just days before the general election, Jeremy Corbyn said he was “looking at ways” to reduce current student debt.

Should I vote Labour? Corbyn's biggest policies explained Show all 9 1 /9 Should I vote Labour? Corbyn's biggest policies explained Should I vote Labour? Corbyn's biggest policies explained Brexit Labour is committed to leaving the European Union but would have different negotiating priorities to the Conservatives. It has said it would have a “strong emphasis” on staying in the single market and the customs union. German Chancellor Angela Merkel and leading figures in Brussels have been unambiguous that membership of the single market is impossible without free movement. PA Should I vote Labour? Corbyn's biggest policies explained Immigration The party would drop “bogus immigration targets” but move to a managed system of migration favoured by many leave voters. It has said this “may include employer sponsorship, work permits, visa regulations or a tailored mix of all these”. Getty Should I vote Labour? Corbyn's biggest policies explained The Economy Labour’s manifesto commits to balance government spending with the amount raised by taxation, which can mean little more than significant tax increases. The greatest burden will fall on higher earners but they cannot meet demand on their own. It has also promised to bring rail companies back in to public ownership and cap fares. The party would also renationalise Royal Mail. It also promises a “transition” to publicly owned energy. Peter Byrne/PA Should I vote Labour? Corbyn's biggest policies explained Tax No one earning under £80,000 would pay any more in national insurance or income tax. It would raise corporation tax, from the current low of 19p to 26p. This higher rate would still be a competitive internationally, but the government is currently fighting hard to attract business in the wake of Brexit and they say a low corporation tax rate is crucial. Labour would also lower the top, 45p income tax threshold to £80,000. In theory, this could raise £7bn, but only if higher earnings did not decide to move abroad. Reuters Should I vote Labour? Corbyn's biggest policies explained NHS Labour has promised more money for GP services, free hospital parking for patients, staff and visitors, and to take a million people off NHS waiting lists by guaranteeing treatment within eighteen weeks. These promises will be expensive to keep, and there is no certainty that the party’ s commitment to raising taxes on higher earners, increasing capital gains tax and reversing cuts to corporation tax will be enough to meet the need. PA Should I vote Labour? Corbyn's biggest policies explained Education The party has pledged to abolish university tuition fees and reintroduce maintenance grants and give free school meals to all schoolchildren. PA Should I vote Labour? Corbyn's biggest policies explained Housing Labour’s manifesto commits to building 1m new homes, and would introduce controls on rent rises for private renters. It would also scrap the so-called bedroom tax. Getty Should I vote Labour? Corbyn's biggest policies explained Environment Labour would ban fracking, but, crucially, also supports new nuclear projects. It would also introduce a new Clean Air Act to deal with illegal air quality Getty Should I vote Labour? Corbyn's biggest policies explained Defence Its manifesto says it is committed to the NATO target of 2 per cent spending on defence. It is also committed to the renewal of Trident, even though Jeremy Corbyn has spent a lifetime campaigning against it. AFP/Getty Images

He told NME magazine: “I don’t see why those that had the historical misfortune to be at university during the £9,000 period should be burdened excessively compared to those that went before or those that will come after. I will deal with it.”

Asked how such a policy might be funded, Ms Rayner said: “Jeremy said that’s an ambition – it’s something he’d like to do. It’s something we will not announce that we’re doing unless we can afford to do that.

Labour has also vowed to abolish tuition fees – a policy it says will cost £9.5bn.

Ms Rayner also had firm words for those in her party who are talking of "deselecting" MPs who are not considered fully supportive of Jeremy Corbyn.

She said those talking of deselection, which include new MP Chris Williamson, should think about "who are the real enemy”.

"I don't like anything in the Labour family that disenfranchises any part of our movement. We are a big movement and we’re all the better for it," she said.

"At the moment we should be concentrating on making sure we're ready for the next general election.

"Anyone who talks of deselecting any of my colleagues, quite frankly, they need to think about, actually, who are the real enemy here?

"Who are making the problems for our communities at the moment? Who have made those disastrous policies that are hurting the people that need us the most? It doesn’t help them if we’re fighting each other."