British Prime Minister David Cameron has warned he would no longer be able to guarantee that Britain would remain a member of the European Union if European leaders elect Jean-Claude Juncker as European Commission chief, Germany's Der Spiegel magazine reported.
The European Commission president is selected by EU leaders but must be approved by the assembly, where Eurosceptics from the right made gains in last week's election. The European People's Party, which won the most seats in the vote, chose former Luxembourg prime minister Juncker as its candidate.
In a pre-publication copy of an article, Der Spiegel said Cameron had made his warning on the sidelines of an EU summit starting in Brussels tomorrow, saying that if Juncker became commission president, he would no longer be able to ensure Britain's continued EU membership.
The magazine said participants understood Cameron's comments to mean that a majority vote for Juncker could destabilise his government to the extent that an "in-out" referendum would have to be brought forward.
That, in turn, would most likely lead to the British people voting to quit the EU, it reported.
A spokesman at the prime minister's office declined to comment on the magazine article.
But Juncker called on the majority of leaders not to bow to pressure from the minority in their decision, according to an advance extract of an article that was due to be published in Germany's Bild am Sonntag newspaper yesterday.
"Europe must not allow itself to be blackmailed," Juncker said, adding that a broad majority of Christian Democratic and socialist leaders in the European Council backed him.
He said he was in favour of getting "all of the other heads of government on board too" in the coming three to four weeks, and offered to hold talks on priorities for the next commission.
Der Spiegel reported that Cameron, who regards Juncker as too federalist and likely to damage his hopes of reforming Britain's EU ties, dismissed the candidate during a recess with the words: "A face from the '80s can't solve the problems of the next five years."
Cameron has promised to renegotiate the terms of Britain's EU membership and if his Conservatives win a 2015 national election to hold a referendum by the end of 2017 on whether or not to remain in the EU.
Last Monday he rejected calls to bring the referendum forward after his party was beaten into third place in European elections by the anti-EU UK Independence Party (UKIP) party.
Bild am Sonntag, which did not name its sources, said French President Francois Hollande was also trying to prevent Juncker from getting the job of commission president and instead wanted a French person for it.
The newspaper said Hollande had last week told German Chancellor Angela Merkel he urgently needed a signal for his government, given the strong performance of the far-right National Front in the European elections, adding that he had suggested his former finance minister, Pierre Moscovici, for the job.
But Juncker said he was "optimistic about being chosen as the next … president by mid-July".