Grammar schools in Kent and Medway could be forced to offer places to children with lower 11-plus marks to increase the number of poorer brighter pupils in selective schools.

The government is reported to be considering the radical plan to counter the claim that grammars are dominated by pupils from better-off families and to improve social mobility.

It comes after the Chancellor announced a £320 million fund for 110 free schools, some of which could be grammars.

The idea of grammars being required to adopt some kind of quota system for brighter children from deprived backgrounds is designed to tackle the issue of social mobility but is likely to be controversial.

The government is said to be considering the option when it publishes a White Paper on education, along with the idea of admitting children at 12 and 13 to reflect the fact pupils develop at different ages.

In Kent, figures show on average just 3% of children on free school meals - the main indicator of social deprivation - attend grammars.

That contrasts with 13.4% in non-selective schools. When it comes to children eligible for pupil premium money there is a similar gap.

A KCC report into social mobility found 6.3% of pupils attending grammar schools receive Pupil Premium, compared to 26.9% in non-selective schools.

The idea of a different pass mark for less well-off children applying to grammars was rejected by a cross-party committee of county councillors investigating ways to improve social mobility in Kent grammars.

The committee did urge the county’s “super selective” grammars - which admit the highest scoring children - to consider setting aside places for poorer brighter pupils who were eligible for Pupil Premium money who passed the 11-plus.

But it said there were better ways to improve access to grammar schools, including extending free school transport - a measure that the government has signalled support for in last week's budget.

Labour county councillor Roger Truelove, who served on the inquiry, said: “It would be invidious for children to go to grammar schools knowing they have been given a favourable assessment.

"We should we be taking steps to ensure children are achieving their full potential after six years in primary education.”

Speaking about the funds for free schools, KCC cabinet member for education, Cllr Roger Gough, said: “If I have a concern it is the issue of free schools delivering their projects on time.

"The approach we have taken [on new grammars] is that where there is demand caused by population growth, we will support them.”

The plan to lift the ban on new grammars has been divisive with 33 Kent headteachers writing to the education secretary Justine Greening to denounce the idea.

However, many of the county’s MPs have welcomed the news.