German right won't snub Merkel in Greek vote: ally BERLIN (Reuters) - Angela Merkel will not need votes from opponents on the left to get a bailout for Greece through the German parliament, a senior ally said on Thursday, despite a growing revolt within the chancellor's conservative coalition. Less than a year before a general election in which she will seek a third term, Friday's vote on measures agreed by euro zone finance ministers this week to cut Greek debt is widely seen as a test of Merkel's authority over her own supporters. Since most opposition Social Democrats and Greens will back the credits, there is no doubt the Bundestag lower house will approve the package; but Merkel would like to contain rebellion in her own ranks, so that she does not need her opponents' help. Volker Kauder, parliamentary floor leader for Merkel's CDU-CSU group, said on Thursday that he was confident the chancellor would achieve that, and added that a big, bipartisan majority in the chamber would also be a positive sign for Europe. "We will have our own majority," Kauder told ZDF television, "The opposition will cooperate and that is a good signal for Europe and for Greece." It is unclear exactly how many may vote against or abstain from among Merkel's Christian Democrats (CDU), their Bavarian CSU allies and coalition partners the Free Democrats (FDP). Government supporters have 330 out of 620 voting seats. Merkel has failed before to secure the 311 votes from her own camp that represent an absolute "chancellor's majority." She may again fall short, but will hope to limit the rebellion to a level where, even were all her opponents on the left to vote against it, the government's bill would still pass. With lawmakers conscious of their own re-election battles, politicians have joined some media commentators in becoming more vocal about the cost of Greek aid to German taxpayers. Many say Greece will eventually fail to repay some of the new credits. In a test vote late on Wednesday, 15 of the 237 lawmakers in Merkel's own conservative bloc voted against the aid package and one abstained - though only about two thirds of lawmakers attended the meeting, participants said. The Free Democrats expect about 10 of their 93 lawmakers to vote against or abstain, said a parliamentary source. That means Merkel is heading for a bigger rebellion than in a Bundestag vote in July on a rescue package for Spanish banks, which saw 22 rebels from her centre-right coalition. The Social Democrats (SPD) confirmed on Thursday that they would back the aid package. In their own test vote, eight of the 146 SPD lawmakers voted against and 13 abstained. The Greens, who have 68 lawmakers, will support the Greek package. The Left Party, which has 76 seats, has said it will oppose. Friday's vote is on a range of measures aimed at cutting Greek debt to 124 percent of gross domestic product by 2020. For the first time, Merkel's government has acknowledged there will be a negative impact on the federal budget due to lost revenues. Finance Minister Wolfgang Schaeuble insists in public that a writedown of debt by Greece's public creditors would be illegal. But fears are growing, even among Merkel's own party ranks, that it may be unavoidable in the longer term. Kauder reiterated that such a move, known as a haircut, was illegal. Asked if it would be a next step, possibly in 2016, he said: "I can say that a haircut is not conceivable in 2016." German economist Hans-Werner Sinn, a long-time critic of aid to Athens who argues that Greece should leave the euro zone, disagreed and said a haircut would come. The whole thing is a bottomless pit. It makes barely any difference, in my view, if you talk about loans or if you just call them gifts from the start," Sinn, head of the Munich-based Ifo think tank, told German radio. Additional reporting by Andreas Rinke and Hans Busemann; Editing by Stephen Brown and Alastair Macdonald