Theresa May should end the 11-plus and allow pupils to join a new generation of grammar schools at different ages, a Tory activist group backed by three cabinet ministers has said.

Conservative Voice has written to the Prime Minister and Justine Greening, the Education Secretary, saying that the age limit is “far too restrictive”.

The group, which was co-founded by new cabinet ministers David Davis and Liam Fox, also wants the first 20 new grammar schools created in deprived parts of Britain to boost social mobility.

The ambitious blueprint is an attempt to create a grammar school system for the 21st century which would boost “choice, opportunity for all and aspiration” according to backers.