Professor Graham Galbraith made the comments after itÂ emerged on Thursday that at least one university had promised a financial incentive for students with unconditional offers.
He told the The News' sister paperÂ i: '˜It is a competitive market and I want the very best students to come here.
'˜I am conscious and I hear from school partners a real sense of concern that unconditional offers will mean students won't make any effort at all.
'˜That doesn't do any good either.'
Universities offering clearing places must '˜put the student first'Â and not award spots simply to fill up courses, the head of a new higher education watchdog has warned.
Nicola Dandridge, chief executive of the Office for Students said there is a '˜danger'Â that students may be unable to cope if they are given places on courses that exceed their ability.
Universities are in fierce competition to attract students after a fall in overall number of people applying for higher education, which could be an advantage to anyone receiving their A-level results on Thursday.
However Ms Dandridge said it was important students have '˜both the ability and the support they need to access and succeed on a degree course'.
'˜While universities often allow students in with lower grades than advertised, it is important they do so with the student's interests at heart,'Â she told The Times.
'˜Lower offers are not appropriate for every student and the danger if grades are lowered drastically simply to fill places is that students may not be ready for the demands of the course and they drop out.
'˜Anyone offering places through Clearing should put the student first.'
Clearing is the annual process that allows students without a university place, or who want to switch to a different one, to search for and find a degree course with availability.
A Press Association snapshot survey suggested that the day before results were due to be released, more than 26,000 courses were available in Clearing for students in England only.
More than half a million students in England, Wales and Northern Ireland are receiving A-level results on Thursday.
However Ucas said the number of people who have applied to UK higher education courses for 2018 has dropped by around 11,000.
The admissions organisation said it believes the 2 per cent drop, bringing the total to 590,270 compared to the same point last year, is due to there being 18,000 fewer 18-year-olds in the UK population along with fewer applications from older UK-based students.
University leaders suggested that there could be more people who are using Clearing this year to apply to university for the first time.
Ucas has urged prospective students to think carefully about what they want to do and where they want to study, as well as whether they meet the requirements to be accepted on to the course.
Competition among institutions to attract students has also been blamed for soaring numbers of teenagers being given guaranteed degree places, known as '˜unconditional offers'.
More than a fifth of teenagers were handed at least one '˜unconditional offer'Â this year, according to Ucas data.
The surge triggered warnings that the credibility of the university system is being undermined and students' futures put at risk.
The Association of School and College Leaders urged universities to stop the practice, arguing that such offers can lead to students making less effort in their A-levels, which could damage their job prospects later on.