Students can gain degrees after completing as little as a third of their courses by paying universities to assess their life experiences and offset them against teaching and assessment.
The Quality Assurance Agency is drawing up guidelines on the use of the Accreditation of Prior Experiential Learning (Apel) after it emerged that some universities waive as much as two-thirds of courses through Apel.
Leisure and voluntary activities are often counted as well as work experience. In one case, recovering drug addicts had their experiences of coming off drugs assessed.
Alan Smithers, professor of education at Liverpool University, said: "The idea that you can be excused quite a chunk of your course on the basis that you've gained life experience is odd in the extreme.
"The point of higher education is to add to your general life experience. And charging money for it is a worrying step in the direction of those degree mills that send you a certificate if you send them a few thousand pounds and your CV."
Concerns about Apel practices emerged after a meeting with university managers hosted by the QAA. Its report on the meeting says: "The minimum and maximum proportions of study (through) Apel permissible for the award of a qualification... varied between HEIs, levels of study and qualification."
The THES has learnt that up to two-thirds of some courses can be waived through the Apel scheme at some institutions, including Anglia Polytechnic University. A spokesman for Anglia said students had to prove the outcome of their experiences through a rigorous process that was "matched closely with the outcome from the taught programmes".
The two-thirds rule is also understood to apply at De Montfort University.
A spokeswoman said that Apel students were carefully assessed and had to complete the entire final year of the course to gain an honours degree.
"It's not an easy option for a student," she said.
"Experiential learning" can include almost any relevant experience. It most commonly involves work experience such as management and accountancy.
However, Anglia advises students that experience as a holiday lifeguard, for example, could offset work towards a degree in sport science, but not any programme where the experience is not directly relevant.
Geoffrey Alderman, academic dean of the American Intercontinental University in London and former quality chief at Middlesex University, said: "It is a very controversial area because it is all very subjective.
Someone has to judge what non-certificated learning represents in academic terms. It may be that some institutions are not being as rigorous as others," he said.
Paula Cleary, a research fellow at Glasgow Caledonian University who has studied the practice for the European Union, said it could apply to "a wide range of personal and social experiences". She said an access to higher education course at Glasgow Caledonian allowed recovering drug addicts to use their experiences to offset formal learning.
"It was for a social sciences degree course and the kind of experiences they had had were relevant: they had had to gather information to learn about how to cope and they had to undergo the process of counselling, for example," she said.
She said Apel had many benefits, especially in the field of widening access but it needed to be properly regulated to ensure that it was not devalued.
In some cases, assessment amounted to little more than an informal meeting where a tutor "simply discussed the student's experiences and mapped it against a module or course unit", she said. In best practice, formal portfolios were developed and assessed.
The QAA's paper warns that Apel charging policies vary "hugely" between institutions: "It is important for students, stakeholders and employers to clearly understand that the charging of a fee does not represent 'buying credits'. Any fee/charge is made in relation to the assessment process."
Some universities allow Apel to be double counted towards more than one qualification, sometimes even where awards are very similar, the QAA says.
"Participants reported that there was currently insufficient shared understanding of the processes/issues and good practice in Apel to have confidence that comparable approaches are being used across the sector. A common framework could facilitate consistent practice," it adds.
The QAA will issue draft guidance for consultation this autumn.