LONDON (Reuters) - Britain's pro-EU former Labour Prime Minister Tony Blair said on Wednesday he felt a "huge stab of anxiety" about the prospect of an in/out referendum on the European Union.
His Conservative successor David Cameron has pledged to give Britons a referendum choice on whether to stay in the EU if he wins an election in 2015.
Speaking from the World Economic Forum in Davos, Switzerland, Blair told Sky TV that Britain's eventual exit from the EU was now on the agenda.
"The thing that sends a huge stab of anxiety through any of us that believe that Britain's place in the 21st Century has got to be as a key player in the largest political union, the biggest business market in the world, is that we're now putting on the table the prospect of Britain leaving Europe in a referendum in four or five years' time," he said.
"Why would we do that now? We don't know what the rest of Europe is going to propose by way of changes resulting from this euro crisis, we don't know yet the detail of what we're going to argue in Europe," he added.
"Surely what is better is to have that debate, try and shape the process in Europe and then decide where we are."
Blair said he agreed with Cameron when he said in a landmark speech earlier on Wednesday that reform was needed in Europe.
"Ninety percent of that speech is ... the British Prime Minister addressing the British national interest," he said.
"It's the climax to the speech (the referendum pledge) that I'm afraid is really about the internal European problem in the Conservative party and how they placate this UKIP party."
The Conservatives have long argued amongst themselves about whether Britain should be an EU member, a division eagerly exploited by the small but vociferous anti-EU UK Independence Party (UKIP) which is rising in opinion polls.
Blair added: "There's got to be a compelling reason to put that (referendum) question on the agenda. I don't see that compelling reason now."
(Reporting by Stephen Addison Editing by Maria Golovnina)