The government should pay for children from poor backgrounds to go to top public schools, Lib Dem deputy leader Vince Cable has said.
Mr Cable said he realised the plan would be 'controversial'
The party has been setting out plans to give schools taking children from the poorest 10% of families extra cash.
But speaking at a party conference fringe meeting, Mr Cable said the "pupil premium" should go much further.
"If someone from a poorer background wants to use the pupil premium to go to Eton we should let them," he said.
Mr Cable said he realised such a policy would be "controversial" but drastic action was needed to kick start social mobility, which the meeting heard had ground to a halt under Labour.
During the 1980s and 1990s the Lib Dems bitterly opposed the Conservatives' assisted places scheme, which offered gifted children free or subsidised places at independent schools.
Labour abolished the programme soon after taking power in 1997, claiming it was elitist and wasteful of public funds.
'Made to work'
"Maybe we should take this one step further and say, why can't this premium be used by these kids and these families to go wherever they want," he told the audience.
"I mean, if they want to use it to go as part payment to get into an independent school, well why not? We'll back them up."
Mr Cable said he recognised the idea could make some activists uncomfortable.
"There will be a lot of argument that we are recreating the assisted places scheme ... I can see all kinds of pitfalls for it.
"But I think with imagination and the right instincts that it could be made to work."