By Katherine Sellgren
BBC News education and family
The survey found 85% of 18 to 24 year olds wanted to see more grammars
A growing number of people want to see more grammar schools, despite a lack of support for them from the Labour and Conservative parties, a study suggests.
A survey commissioned by the National Grammar Schools Association (NGSA) found 76% of adults supported the idea of new grammar schools being built.
A similar survey in 2006 found 70% of adults were in favour of the expansion of academically selective schools.
The NGSA is now calling on politicians to open more where parents want them.
The Labour government banned the opening of new grammar schools when it came to power and the Liberal Democrats say they would not open any new ones.
In 2007, David Cameron controversially announced the Tories were withdrawing their traditional support for grammars.
But these schools remain popular with parents, many of whom coach their children intensively to pass the 11-plus that determines whether or not they get a place.
Many commentators, including the former chief inspector for schools, Chris Woodhead, see grammar schools as crucial in contributing to social mobility.
Currently there are 232 grammar schools in the UK - 164 in England (out of a total of 3,361) and 68 (out of a total of 223) in Northern Ireland. There are no grammar schools in Wales and Scotland.
The survey, carried out by ICM, found 85% of 18 to 24-year-olds, many of whom will be first-time voters, wanted to see more grammar schools.
Robert McCartney, chairman of the NGSA, said: "It's unbelievable that none of our three largest political parties seriously supports either existing grammar schools or the idea of opening new ones where there's parental demand.
"If they want our votes, they should offer what the public wants."
A spokesman for the Department for Children, Schools and Families said: "We don't support academic selection.
"The evidence is clear that sorting children into sheep and goats at 11 works well for the minority of children who go to grammars, at the expense of the majority who don't.
"We want to improve all schools - that's why we target the most deprived areas through the massively successful Academy and National Challenge programmes.
"We changed the law so academic selection cannot be extended outside the tiny minority of schools where it still exists. There are absolutely no plans to change that."
A spokesman for the Tories said: "We set out our policy on grammar schools in 2007 and it hasn't changed."
ICM interviewed a random sample of 1,015 adults aged 18 and above in early February.