University acceptance rates among students who achieve C and D grades at A-level are on the increase, according to the latest official statistics, revealing that record proportions of English and Scottish 18-year-olds were accepted into university this year.

The figures, published by the university admissions service Ucas, would fuel fears of a bums-on-seats approach to recruitment by some institutions, as they struggle to fill courses due to a decline in the number of 18-year-olds.

The data showed that of the 44,000 students who achieved three Cs or lower at A-level this summer, the university acceptance rate was 84% compared with 79% five years ago. Applicants with A-level points equivalent to three Ds had an acceptance rate of over 80%.

The proportion of applicants missing their predicted grades has also been growing, and they have missed them by a greater margin. According to Ucas, the proportion of placed applicants achieving fewer points than predicted has risen from 73.3% in 2013 to 76.8% this year.

The proportion of those missing their predicted grades by three or more grades has increased by 3.3 percentage points since 2017, and 11.5 percentage points since 2013. Clare Marchant, the Ucas chief, said universities should be “mindful” of accepting applicants with lower grades.

She said: “We’re working with schools and universities to improve the accuracy of predicted grades, exploring the different ways teachers make predictions, and how they are used by admissions teams when making offers. Our good practice guide will be published in the new year.”

The Ucas figures were released as the new universities’ regulator, the Office for Students, published what it described as “ambitious” targets, challenging universities “to eliminate the gaps in access and student success within 20 years”.

The targets aim to eliminate gaps in entry rates at the most selective universities between the most and least represented groups; drop-out rates between the most and least represented groups; degree outcomes between white and black students, and degree outcomes between disabled and non-disabled students.

Damian Hinds, the education secretary, called for specific action to improve access for white working-class children, and to ensure that groups of students who were currently less likely to complete their courses, such as black students, stay on until the end of their studies.

He said: “I see no reason why race or background should be a factor in whether a student can access and benefit from the opportunities that higher education provides – and we must all share a collective endeavour to tear down these barriers where they exist.”

Sarah Stevens, the head of policy at the Russell group of universities, said an average of £1,100 was spent per student per year on programmes to widen participation at institutions in the Russell group, adding: “We strongly urge the government to protect this level of investment through its current review of university funding”.