Half of Britain’s students are struggling to pay their rent as spiralling housing costs prompt warnings that the university accommodation system has reached breaking point. As the last-minute scramble for accommodation for the next academic year gets under way, the National Union of Students described the cost of housing as at an absolute crisis point.

“Students are facing a housing crisis with an ever-narrowing gap between their incomes and what they are expected to pay in rent,” said Shelly Asquith, the NUS vice-president of welfare. “There needs to be enforced rent controls to put an end to this.”

Between 2010 and 2013, rents rose 25%, according to the student housing charity Unipol. This compared with rises in the wider rental market over the same period of 13%, according to Homelet. The latest Unipol data, to be published in November, is expected to show further rises of around 7%.

A maintenance loan of up to £8,000 in London or £5,500 outside the capital is available to students for help with living costs, but the NUS is concerned that the sky-high costs of housing mean this is now being almost being completely eaten up by rent.

NUS figures for the academic year just gone show a typical £8,000 a year shortfall between student living costs and their income from loans and the maintenance grant.

“Sadly, it is no surprise that, with sky-high rents, students are struggling to find accommodation in the private rental sector,” said Roger Harding, Shelter’s director of communications, policy and campaigns. “And even when people do find somewhere, we too often hear from students dealing with issues like poor conditions, unprotected deposits and unfair terms in tenancy agreements.”

The figures from Shelter’s Private Tenant Survey, given exclusively to the Observer, show that 50% of students are struggling with rent and 40% of student renters had borrowed money from any one of a range of sources to meet their monthly rental payments, in the last year.

Andrew Green, an A-level student who got better than expected results last Thursday, will be heading to Portsmouth to study law in September. He said that his rent, £120 a week in halls, was a shock.

“This massive expense just for living was completely new to me,” he said. “My student loan does not cover the cost of my accommodation by a considerable amount – there’s roughly a £30 deficit a week.”

The NUS attributes a large part of the rise in rents to the huge growth in private sector student housing developments coupled with a sell-off by the universities of their own low-rent stock.

“Universities have failed to secure affordable accommodation and have either invested in expensive stock themselves or sold off old stock to private developers,” says Asquith. “It has become such an explosive market and is cutting huge amounts of poorer students out of university.”

The NUS’s latest report, Debt in the First Degree, published last week, looked at the attitudes of the first £9,000 fee-paying graduates. Just under a third said the cost made them consider whether or not to attend university.

However, with the removal of the cap on student numbers, the number of undergraduates who are looking for accommodation has reached record levels this year.

Student numbers are expected to continue to rise, though it is anticipated that many poorer students may be put off from next year, when the maintenance grant is replaced by a loan.

The majority of the new accommodation needed will be provided by private companies, which in 2013 provided 80% of new bed spaces, according to Unipol. Already this year private investment in student digs has reached record levels with billions poured into the market by Russian, Middle Eastern and Canadian investors.

With flatscreen TVs and en-suite bathrooms as standard, private sector accommodation is typically more expensive than university-owned accommodation. At the same time, the lower-cost rooms available from education institutions have got much more expensive, rising 23% in price since the academic year 2009-10, according to Unipol. This means some institutions no longer have any low-cost rooms for their poorer students.

“The past few years have seen huge growth in ‘luxury’ student accommodation, and it is not coincidental that this has come at the same time as the increased marketisation of higher education,” said Tom Robinson, welfare and international officer at the University of London’s union.

“It is symptomatic of a society that sees education not as a right and a social good, but as an investment in future career options, and the ‘student experience’ as a package to be sold to entice whoever is able to pay the most money.”

A spokesperson for the Department for Business, Innovation and Skills said: “The government is committed to widening access to higher education and anyone with the ability to succeed should have the opportunity to participate, regardless of their background or ability to pay. Following changes announced in the budget, we will be providing students with more money in their pockets than ever before to help with living costs while studying.”

• This article was amended on Sunday 16 August to include a comment from the Department for Business, Innovation and Skills.