US could have bugged Angela Merkel's Nokia mobile phone for four years The controversy is dominating a European Union summit being held in Brussels today and tomorrow. Sigmar Gabriel, the chairman of the Social Democratic Party, said the revelations threatened EU-US free trade talks. "It is hard for me to imagine negotiating a free trade deal with the United States to the end if the freedoms and personal rights of citizens in Europe are endangered," said Mr Gabriel, whose party is likely to join a coalition soon with Mrs Merkel's Christian Democratic Union. His anger was echoed by many other Germans, who feel such eavesdropping would mark a betrayal by the country that did most to defend West Germany from Communism during the Cold War. "The Americans are and remain our best friends but this is a no go," Defence Minister Thomas de Maiziere told German television. He said he had long thought his mobile phone was being tapped, "but not by the Americans." Earlier in the day, Germany summoned the US ambassador to Berlin over the allegations. Guido Westerwelle, the foreign minister, will meet with John Emerson later on Thursday, in a highly unusual step between the decades-old allies. The very idea of bugging is particularly sensitive in Germany, dredging up old memories of the Stasi in former East Germany, where Mrs Merkel grew up. "The American ambassador was summoned for talks with Foreign Minister Westerwelle this afternoon," the spokesman said. The position of the German government will be presented clearly. Chancellor Merkel called President Obama on Wednesday demanding answers after reports emerged that the US may have been monitoring her phone. The reports emerged from Der Spiegel. A White House spokesman said it is not now listening in on Mrs Merkel, but did not deny the possibility her communications may have been intercepted in the past. The US did however flatly deny ever monitoring the communications of David Cameron, the Prime Minister. The allegations have sparked outraged in Germany and Mrs Merkel's spokesman Steffen Seibert said in a statement that she "made clear that she unequivocally disapproves of such practices, should they be confirmed, and regards them as completely unacceptable." She had demanded "an immediate and comprehensive explanation" from Washington, the statement said. "Among close friends and partners, as the Federal Republic of Germany and the US have been for decades, there should be no such monitoring of the communications of a head of government," the statement added, indirectly citing Mrs Merkel's comments to Mr Obama. This would be a serious breach of trust. "Such practices must be stopped immediately," the German chancellor told Mr Obama, the statement said. Thomas de Maiziere, the German defence minister, said Europe simply can't return to business as usual in its relations with the US, adding that it would be "really bad" if the allegations were confirmed. The row comes days after France summoned the US ambassador to Paris to demand an explanation to reports that America swept up 70 million French telephone records in a month including politicians and business leaders. France is expected to put US bugging on the agenda of a European Union summit later on Thursday. Viviane Reding, the European commissoner for justice, said: "The most recent spying scandals show data protection must apply to everyone - whether we are taking about citizens' emails or Angela Merkel's mobile phone. We now need big European rules to counter big fears of surveillance. At the summit today, Europe's heads of State and Government must follow words with action.