David Cameron is prepared to consider a referendum on the UK's EU relationship, but only when the time is right, he has written in the Sunday Telegraph.
In the article, the prime minister said he wanted a "real choice" for voters but said an immediate in/out referendum was not what most wanted.
The Lib Dems said the article addressed internal Tory divisions, adding there is little public appetite for debate.
Nearly 100 Conservative MPs have called for a poll during the next Parliament.
In a letter to the prime minister, they urged him to make it a legal commitment to hold a vote on the UK's relationship with the EU.
A Liberal Democrat source said Mr Cameron was "perfectly entitled", as Tory party leader, to set out his views on a possible referendum after the 2015 general election.
But, the source said, there is little public appetite "for an abstract discussion about a referendum on an undefined question at an unspecified time in a future parliament".
Labour accused Mr Cameron of engaging in "party management" saying the eurozone crisis was the "big issue".
Foreign Secretary William Hague, speaking on BBC One's Andrew Marr Show, said there was "a very powerful case" for a referendum if other member states agreed a closer union following the eurozone crisis.
But, he said, the time to decide would come when it was clear how Europe would develop and how the UK's relationship with the EU could be made "better".