John Bercow has backed an in-out referendum on British membership of the EU so the issue can be "laid to rest".

The Commons Speaker risked venturing onto a key general election battleground by reportedly saying there was a "strong case" for a decisive vote "at some suitable point".

The comments come with parties engaged in fierce clashes over whether a referendum is necessary and when it should be held.

David Cameron has pledged a renegotiation of British terms and national ballot by 2017 if he wins next year's general election, and is trying to force through backbench Tory legislation guaranteeing the commitment.

Ukip's recent surge in local and European polls has been attributed in part to their Euroscepticism.

But both Labour and the Liberal Democrats have stopped short of promising a referendum unless there are proposals for a further transfer of powers to Brussels.

The Speaker traditionally maintains neutrality between parties, not least to avoid suggestions of bias when he chairs parliamentary debates.

However, taking questions after delivering a keynote address on Digital Democracy yesterday evening, Mr Bercow is reported to have said: "I'm not going to get into the question of the timing because I will leave that for party leaders, but I do happen to think there is quite a strong argument, actually, for there to be a referendum at some suitable point on British membership of the European Union because it seems to me otherwise our membership is fundamentally insecure.

"And there is a lot to be said for resolving the issue one way or the other.

"Now I know there will be Eurosceptics who want a referendum but there is equally a perfectly respectable case for people who consider themselves very pro-European Union or at any case pro-remaining within it who argue for a referendum as well on the grounds the matter needs to be laid to rest."

Mr Bercow - who has previously indicated he favours Britain staying in the EU - said it was a "powerful point" that people under 57 will not have had the opportunity to express their views on the issue.

Mr Cameron is set to face questions on his efforts to convince fellow EU leaders of the need for fundamental reforms when he comes to the Commons today.

The Prime Minister has been engaged in a stand-off with German Chancellor Angela Merkel and others after making clear he does not want continuity candidate Jean-Claude Juncker to become the next President of the European Commission.