The Government is planning to open new grammar schools, a minister has inadvertently revealed.
The paper, signed by the Department for Education's most senior civil servant, said Education Secretary Justine Greening planned to launch a consultation into opening new grammars.
Her "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.
The document, which was photographed being carried into No 10 Downing Street by deputy Lords leader Earl Howe 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."
The Government refused to comment on the document but did not deny its contents.
A spokeswoman said: "The Prime Minister has been clear that we need to build a country that works for everyone, not just the privileged few.
"We are looking at a range of options to allow more children to access a school that lets them rise as far as their talents will take them.
"Policies on education will be set out in due course and it would be inappropriate to comment further on internal government documents."
The creation of new grammar schools was outlawed by Labour under former prime minister Tony Blair.
But reports last month suggested Prime Minister Theresa May was considering 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, yesterday dismissed the selective model and said it would fail the poorest children.
Commenting on the briefing note, 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.
"The Tories have overseen a school places crisis, the highest rate of teachers leaving the profession in a decade and over half a million pupils in super-sized classes. These issues should be her priority, not harking back to a golden age that never existed.
"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.
"The Government should be ashamed of themselves.
"If they think this is the right thing to do, they should bring it to Parliament and win the argument."
Labour leader Jeremy Corbyn reiterated his opposition to the plans and suggested the Tories would have to bring back secondary modern schools in conjunction with new grammars in England.
Speaking at a press conference alongside reggae band UB40, Mr 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."
UB40's Brian Travers backed Mr Corbyn.
"Surely a level playing field is what we should be searching for," he said.
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".
NUT general secretary Kevin Courtney said: "Opening new grammar schools would not only be a backward step but is also a complete distraction from the real problems facing schools and education.
"For every grammar school there are three or four 'secondary modern' schools.
"All the evidence makes clear that segregating children in this way leads to lower academic standards."
Mr Courtney said disadvantaged students, such as those eligible for free school meals or who live in poorer areas, were less likely to earn a place at a grammar.
Asked whether the PM was planning an expansion of grammar schools, Mrs May's official spokeswoman told a Westminster media briefing: "Both the Prime Minister and Education Secretary have spoken in recent weeks about what our approach is focused around, which is building a country that works for everyone, not just a privileged few.
"We are looking at a range of options to make sure children can access a school that lets them rise as far as their talents will take them.
"We will set out our policy in due course."
Unison, which represents thousands of education workers, said new grammar schools would make the system more elitist.
General secretary Dave Prentis said: "This policy will further damage the UK's underfunded education system.
"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.
"If the government really cared about making the country fairer then decent pay for education workers would be its priority, rather than introducing further elitism into the system."