The Conservative leader of Kent County Council has voiced concern that some grammar schools are choosing to accept children on lower pass rates as a way of boosting their budgets.

Cllr Paul Carter did not identify specific schools but said the issue was a particular problem in east Kent, where he said that some grammar schools were dropping their test scores to allow for more pupils.

It comes as the Department for Education has rejected a Freedom of Information request from the KM Group to provide a list of schools that had applied for a share of a £50 million fund to expand.

The government said it was not in the public interest to disclose the list, thought to include a handful of grammars in Kent.

Cllr Carter warned there was a risk that grammars were diluting academic standards and potentially harmed non-selective schools nearby.

It comes amid related claims that some schools are letting more children applying for grammar schools on appeal despite not passing the Kent test.

Kent is the largest selective area in the country, with 32 grammars.

Mr Carter said: “Many now set their own pass rate and will fill the school up no matter what. If you were a governor of a grammar school and every pupil that comes along is [worth] nearly £5,000, you want to try and fill the grammar school up and have full forms of entry.

“The tendency now is to set a pass rate that fills the grammar school. I think you have got to be careful that you don’t dilute the specialism of grammar schools, which are there to provide a learning environment for the highly academic students.”

His remarks are thought to reflect private concerns of education bosses at KCC that a small number of grammars have this year significantly increased their intake by allowing large numbers of appeals to go unchallenged.

While the county council aims for about 25% of pupils to go to grammar, the figure stands at nearly 32%.

Mr Carter’s comments were described as ludicrous by Comprehensive Future, the campaign group that opposes school selection.

Spokesman Joanne Bartley said: “It's ludicrous that a leader of a selective county is complaining about the inevitable problems of grammar school selection. Kent County Council set the selected percentage to 25% back in the late nineties - as if that exact percentage made any sense.”

“And of course the schools just do as they please. It just proves that there is no logic to grammar school selection,” she said.

Several grammars operate their own tests alongside the Kent test, which are used as a way of filling up places that would otherwise be left vacant.

In refusing the list of grammars who bid for expansion money, the Department for Education argued that it was “part of the effective conduct of public affairs that the general publication of information is a conveniently planned and managed activity within the reasonable control of the public authority.”