BERLIN, Aug 8 (Reuters) - Members of German Chancellor Angela Merkel's Christian Democrats (CDU) have called on parliament to grant gay couples the same tax benefits as married heterosexuals, a shift for the conservative party that has fuelled anger among their Bavarian coalition partners.
Family Minister Kristina Schroeder has backed a call from a group of 13 CDU lawmakers who are appealing for a change in the law to put gay couples on an equal footing in terms of tax breaks, saying now was the right time for a change.
"In lesbian and gay life partnerships, people take long-term responsibility for each another and live according to conservative values," said Schroeder.
Same sex partnerships have been legal in Germany since 2001, but gay couples do not enjoy the same tax benefits as heterosexuals.
The move, which comes about three months after Barack Obama became the first U.S. president to back same-sex marriage, drew swift support from Merkel's Free Democrat (FDP) coalition partners and the opposition Social Democrats (SPD).
However, the CDU's Bavarian sister party, the predominantly Catholic Christian Social Union (CSU), railed against the idea.
The CSU accounts for about 20 percent of Merkel's conservative bloc in parliament and could stop any legislation. The party has given Merkel a headache with its opposition to euro zone bailouts and its rhetoric is getting even tougher in the run-up to a difficult state election next year.
Its members lined up to say such a move would undermine the sanctity of marriage.
"Marriage between a man and a woman must be especially protected because it is fundamentally oriented towards the propagation of life," said Gerda Hasselfeldt, the head of the CSU's parliamentary group in Berlin.
Another obstacle may come from CDU Finance Minister Wolfgang Schaeuble, a conservative from the southern Catholic state of Baden-Wuerttemberg.
An extension of the tax breaks to Germany's 23,000 registered gay couples would cost 30 million euros ($37 million)a year, said a finance ministry spokeswoman, a fraction of the 20 billion euros in tax breaks for heterosexual married couples.
However, she added that the issue should be put on hold until after a long-awaited ruling by the Constitutional Court on income tax differences.
The court's rulings in a series of cases in the last few years, including one on Wednesday, indicate it will say gay couples should be treated equally to heterosexuals in terms of income tax. A broader decision on the issue is expected next year which may force the government to act.
It was largely due to pressure from the court that the CSU agreed to a pledge to abolish tax disadvantages for same-sex couples in the three-way coalition agreement with the CDU and FDP, a party which champions individual rights.
But that a group of lawmakers in the CDU, which has Catholic roots, feels it can push the issue underscores Merkel's willingness to break some traditional tenets of her party.
In her seven years in office, Merkel has shifted her conservative party's policy platform significantly to the left - from abruptly accelerating a nuclear phase-out to backing a minimum wage and abolishing army conscription.
Such moves, on top of broad agreement with the SPD on the euro zone debt crisis, have led analysts to speculate that she will pair up with the biggest opposition party for a "grand coalition" again after next year's election.
Polls suggest that outcome, which would be a repeat of the coalition she led between 2005 and 2009, is a strong possibility, due largely to a slide in support for the FDP.
The SPD raised the pressure on Merkel on the gay couple question on Wednesday, saying it would draw up a cross-party motion on the issue to see if the conservatives would agree. ($1 = 0.8052 euros) (Additional reporting by Matthias Sobolewski; Reporting by Madeline Chambers; Editing by Noah Barkin and Myra MacDonald)