The number of top degrees has more than doubled in the past decade
Universities are turning a blind eye to cheating to boost degree results, a leading academic has said.
Buckingham University's Professor Geoffrey Alderman says league tables create pressure to award high marks.
The number of first-class honours degrees awarded has risen by more than 100% in the past decade. The number of undergraduates is up by just over 40%.
Universities UK, which represents vice-chancellors, said all courses were subject to regular internal monitoring.
Professor Alderman, who used to set standards at the University of London, will say in a lecture that academics are under pressure to turn a blind eye to plagiarism and "mark positively", which could lead to a collapse in degree standards.
9,200 students caught
Most common penalty to re-submit work
More students received verbal reprimand than were expelled
Despite the rise in first class degrees, Professor Alderman says standards have actually dropped.
He also says universities have been lenient with overseas students because they rely on them heavily for their fees.
Professor Alderman will say: "Standards of English literacy at UK universities are often poor.
"To compensate for this, lecturers are pressured to 'mark positively'. This is particularly true in relation to international students, whose full-cost fees are now a lucrative and essential source of much-needed revenue.
He will add: "I have heard it seriously argued that international students who plagiarise should be treated more leniently than British students because of 'differential cultural norms'.
"It is indeed rare, nowadays, for habitual plagiarists to be expelled from their universities."
A study published recently found only 143 students caught cheating were expelled out of 9,200 cases - despite almost all universities threatening expulsion as a sanction.
Universities UK said the system for assuring quality and standards in higher education was "sound and well-established".
A spokesman added: "It is also well respected internationally and has informed and influenced parallel developments worldwide."