The “unsustainable and ultimately pointless Ponzi scheme” that higher education has become is burdening graduates with debts and must be radically reformed, Theresa May’s former chief of staff has said.

Nick Timothy said many school leavers receiving their A-level results on Thursday are being “forced” into expensive degrees that fund a “gravy train” for university bosses.

The adviser warned that without radical reform the system will continue to “blight young people’s futures”, leaving them carrying “millstone” debts of £50,000 – the majority of which will not be paid off.

Branding conventional wisdom that university degrees are best for the economy as mistaken, Mr Timothy called for the use of technical qualifications such as apprenticeships to be expanded as part of a new system.

Writing in the Daily Telegraph, he said: “Today, hundreds of thousands of young people receive their A-level results, and it is difficult not to worry about their future.

“The fortunate among them – those studying at the best universities and taking the best courses – may go on to prosper.

“But those who choose the wrong institutions and courses will see little benefit, while those who do not go to university – still a majority of young people – will be neglected.”

A July report by the Institute for Fiscal Studies found most graduates will still be paying off student loans into their 50s, and three-quarters will never clear the debt.

“We have created an unsustainable and ultimately pointless Ponzi scheme, and young people know it,” Mr Timothy said.

Mr Timothy recognised that it would be too expensive to scrap tuition fees entirely and clear graduates’ debts, calling Jeremy Corbyn’s pledge to “deal with” the issue “wrong and deceitful”.

He also dismissed the introduction of a “graduate tax”, paid for once in employment, as it would still encourage students to take unproductive degrees in the expectation that others will pay.

Mr Timothy supported a system proposed by education policy expert Professor Alison Wolf of offering a “single financial entitlement” to school-leavers.

As well as university degrees the repayable funds could be spent on technical courses with fees capped at a lower level.

This would tempt students away from poor-quality degrees while increasing competition among universities – which would have to lower fees as a result.

Jo Johnson, the universities minister, said university still delivered “extraordinary returns” for students and the system was meeting the Government’s core objectives, although it was always kept under review.

He also told BBC Radio 4’s Today programme he had called for restraint on vice-chancellor’s pay.

“The new regulator, which we’ve recently created to promote value for money in the system, the Office for Students, I’ve asked it to ensure that exceptional pay can only be justified by exceptional performance,” Mr Johnson said.