Several Conservative-linked pressure groups and think tanks have come out in support of Theresa May's rumoured plans to approve a new wave of selective grammar schools.
It comes amid reports that around 20 of the schools could be created in mainly working class areas in an effort to improve social mobility.
The Tory organisations came together in an attempt to refute claims that the Prime Minister would not have the support of enough Conservative MPs for Parliament to approve the new schools.
Those announcing their support include former Cabinet ministers Dominic Grieve, John Redwood and Lord Tebbit.
The organisations backing the move are the Bow Group, Conservative Voice, Conservative Grassroots, Conservatives for Liberty, Parliament Street, ResPublica, Centre for Policy Studies and The Freedom Association.
Former attorney general Mr Grieve said: "It had been my view from my time in Parliament that the education system in my constituency which includes the possibility of grammar school education, offers added value and is of public benefit.
"I welcome the opportunity of seeing this extended elsewhere particularly in areas of social disadvantage."
Mr Redwood said: "Expanding grammar school places will offer more choices and chances to academically gifted pupils from lower income backgrounds.
"It does not damage the many great comprehensives and academies we already have.
"We back selection for those who want to pursue excellence in music, dance and sport, so why not in academic work?
"I do not accept grammars create an insuperable divide at 11."
Lord Tebbit said: "I welcome the Prime Minister's proposal to open more grammar schools, but I hope that will be achieved alongside the creation of a new generation of technical schools and colleges to teach the skills needed in both commerce and advanced manufacturing in a more diverse economy."
Their endorsement comes after backbench Tory Mark Pritchard said the rumoured move would lack political legitimacy as it was not in the Tories' 2015 general election manifesto and would be opposed by a significant number of party MPs.
Opposition parties have reacted with fury to reports that selective education may be back on the agenda, vowing to fight a system which Labour said should be consigned to "the dustbin of history".
The Liberal Democrats will also fight the proposal, leaving the Tories mainly relying on their working parliamentary majority of 17 MPs.
Mr Pritchard's comments followed suggestions that the PM could announce she is lifting the ban on new grammar schools as early as the October Conservative conference.
Mrs May is thought to be a supporter of new selective schools, having backed a grammar school's proposal to open a new "annexe" in her Maidenhead constituency.
And the PM's new chief of staff Nick Timothy has also backed new selective schools in the past.
Mrs May's predecessor David Cameron annoyed some Conservative backbenchers by resisting the creation of new grammar schools, focusing his education policy instead on academies and free schools which do not select on ability at the age of 11.
Any return to the grammar system can be expected to be divisive.
Opponents argue that the 11-plus exam led to elite schools dominated by middle-class children while the majority of young people from poorer backgrounds received sub-standard education in secondary moderns.
A ComRes poll for The Sunday Mirror and Independent found that the majority of Britons (51%) believe grammar schools are good for social mobility.
Around a quarter (27%) opposed grammar schools because they felt they help those who are already privileged.
Despite the majority support for grammar schools, 47% opposed the selection of pupils through an 11-plus exam, while a quarter (25%) favoured keeping the ban on new selective grammar schools in place.