Elite private schools have called for universities to cut back on the use of unconditional offers for undergraduate places over fears that pupils will not be motivated to strive for high A-level grades.

Mike Buchanan, the executive director of the Headmasters’ and Headmistresses’ Conference (HMC), which represents many of the country’s most expensive independent schools, claimed that pupils “take their foot off the gas” after accepting offers that do not require specific A-level grades.

“These youngsters have to carry their results with them for their whole careers,” Buchanan, the former headteacher of Ashford School in Kent, told the Times newspaper.

“I am asking universities to stop using them unless they have interviewed the pupil and got some sense that it would be good for this pupil, or have consulted the school, which has given you the same information.”

Until recently only a small number of school-leavers were given unconditional offers. But the government’s removal of its cap on funded undergraduate numbers has allowed universities in England to expand and aggressively compete for students and their tuition fees.

While there is little recent evidence to show whether pupils with unconditional offers achieve disappointing final grades, private school heads have long been hostile because of the potential impact on their school’s results and league table rankings.

Some employers pay close attention to A-level grades in recruiting for graduate trainee programmes, meaning that students who underperform may later struggle in the job market.

The HMC’s call follows that of Sam Gyimah, the higher education minister, who said in July that the rise in unconditional offers was “completely irresponsible to students, and universities must start taking a lead by limiting the number they offer”.

In most cases, universities make conditional offers, detailing specific A-level grades that applicants need to achieve to take up a place . However, greater competition has seen the use of unconditional offers spread to universities in the more selective Russell Group of research-intensive institutions.

Figures from Ucas, the university applications administrator, show that 7% of the 950,000 offers made this year were unconditional, with about a fifth of the 250,000 applicants to English universities receiving at least one unconditional offer.

Ucas said the offers were more common for older students who already held qualifications, to creative arts course applicants who submit portfolios or attend auditions, and for students with mental health difficulties.

Vice-chancellors have defended unconditional offers as allowing earlier engagement between universities and students, and making it easier to plan courses and accommodation.