Barroso echoes fears over vote on EU David Cameron's plan to renegotiate Britain's EU membership and to put the new deal to a referendum came under renewed fire on Thursday, as senior politicians in Brussels and Berlin echoed concerns raised in Washington. Mr Cameron's long-trailed "big speech" on Europe, expected this month, has unleashed criticism even before it is made, as foreign politicians and British business leaders warn that he is about to embark on a dangerous path. José Manuel Barroso, the European Commission president, appeared to endorse American concerns when he said he feared that an internal fight in Britain could distract the EU at a time of economic crisis. Echoing the warning of Philip Gordon, assistant US secretary for European affairs, that referendums "often turned countries inwards," Mr Barroso said Europe needed to focus on opening up to the world. "What I hope is that debate does not distract us from the very important challenges we have, namely tackling the crisis," he said in Dublin, at the start of the Irish EU presidency. He said London would be critical to free-trade agreements that Brussels is seeking to conclude in the future. "We cannot, in times of crisis, close ourselves to the rest of the world," he said. Meanwhile one of Angela Merkel's closest allies in the CDU party warned Mr Cameron not to try to blackmail the rest of Europe by threatening to block any future EU treaty on eurozone co-operation unless he won a better deal for Britain. You have to ask yourself if it is wise to carry out a referendum. It is certainly possible to convince people of advantages of the EU," said Gunther Krichbaum, the chair of Germany's European affairs committee, on a visit to London. But there is always a risk that the referendum becomes - as Charles de Gaulle put it - less about the question asked and more about the person who's asking it. He added: "You cannot create a political future if you are blackmailing other states. That will not help Britain. The interventions by Mr Barroso and Mr Krichbaum will be regarded by Mr Cameron's Conservative colleagues as entirely predictable, although the public warning from Washington was harder to bear. Mr Cameron's allies admit the Europe speech is turning into a public relations problem, since its contents have been well trailed and are now open to attack from all sides while eurosceptics may find it something of an anticlimax. The prime minister is constrained on what he can say until he makes the speech, expected on January 21 or 22. Even the venue is not finalised: his allies say it may be made in the Netherlands but other options are being considered. In London Nick Clegg, Liberal Democrat deputy prime minister, said Mr Cameron's plans for a renegotiation and referendum were not formal coalition policy but matters for the Tories" 2015 election manifesto. He said Britain's EU membership was vital for jobs and the country's security, adding: "You play with that status at your peril." The pro-European Lib Dems have previously advocated an in-out EU referendum to clear the air, but Mr Clegg refused to repeat the commitment on Thursday, saying it remained to be seen what any new EU treaty might look like.