Theresa May has been accused of elitism and taking education back to the 'bad old days' of the 1950s after plans to open new grammar schools were inadvertently revealed on Downing Street.
A document signed by the Department for Education's most senior civil servant was photographed being carried into No 10 and revealed proposals for a Government consultation on opening new grammars.
It said Education Secretary Justine Greening's 'clear position' is that they should only be approved once ministers have worked with existing selective schools to show that pupils who do not make the grade are not disadvantaged.
Opposition parties and unions reacted angrily, accusing the Government of promoting the interests of a 'select few' and attempting to sneak through the proposal without parliamentary scrutiny.
The Prime Minister's official spokeswoman said the Government was 'looking at a range of options' and insisted Mrs May and Ms Greening want education policy to help Britain 'work for everyone, not just the privileged few'.
The document, which was photographed being carried into No 10 by an unnamed official and is signed by DfE permanent secretary Jonathan Slater, states: 'The con doc (consultation document) says we will open new grammars, albeit that they would have to follow various conditions.
'The SoS's (Secretary of State's) clear position is that this should be presented in the con doc as an option, and only to be pursued once we have worked with existing grammars to show how they can be expanded and reformed in ways which avoid disadvantaging those who don't get in.
'I simply don't know what the PM thinks of this, but it sounds reasonable to me, and I simply can't see any way of persuading the Lords to vote for selection on any other basis.'
Reports last month suggested Mrs May was considering overturning Tony Blair's ban on new grammar schools by sanctioning around 20 institutions in mainly working class areas in an effort to improve social mobility.
The plans have been backed by several Conservative-linked pressure groups and think tanks but have drawn stinging criticism from opposition parties, unions and other independent organisations.
Sir Michael Wilshaw, the Government's outgoing chief inspector of schools, on Monday dismissed the selective model and said it would fail the poorest children.
Shadow education secretary Angela Rayner accused the Government of prioritising the interests of a few of the highest performing pupils at the expense of the majority.
The Labour frontbencher said: 'The cat is out of the bag: behind closed doors the Tories are planning a return to the bad old days of grammars, ignoring all the evidence which has told us time and again that they do not aid social mobility.
'As Michael Wilshaw said yesterday, with every grammar school you open you create three more secondary moderns with it. It's a policy which reveals the truth of this Tory Government: caring only for the few at the expense of the majority.'
She added: 'Labour is committed to an education system for everyone, not just a select few.'
Liberal Democrat education spokesman John Pugh said the proposals appeared to suggest the Government wanted to 'avoid parliamentary scrutiny and an inevitable defeat'.
'This lays bare the desperate lengths the Conservative Party are willing to go to deliver grammar schools through the cloak of expansion,' he said.
'If they think this is the right thing to do, they should bring it to Parliament and win the argument.'
Labour leader Jeremy Corbyn said: 'I am in favour of young people being taught together of differing abilities because that helps them to develop at their own pace but also helps everyone to understand the abilities and values in each other.
'Whilst I have often heard many Conservative politicians talk about bringing back the grammar school I have never, ever heard any Conservative politician ever call for the return of the secondary modern school.'
The National Union of Teachers (NUT) accused Mrs May of 'taking education back to the 1950s, when children were segregated at age 11 and their life chances determined by the type of school they attended'.
Unison general secretary Dave Prentis said: 'Grammar schools are sold as an opportunity to help working class children, but evidence suggests that instead they segregate schooling- putting the greatest opportunities in the hands of more affluent families.'
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here