BERLIN (AP) — A group of lawmakers from German Chancellor Angela Merkel's conservative party called Tuesday for same-sex couples in civil partnerships to be given the same tax breaks as heterosexual married couples, but the idea faced skepticism among traditionally minded colleagues.

Granting gay couples the same income tax breaks enjoyed by heterosexual married couples would add to a string of departures from conservative orthodoxy under Merkel's leadership. Those have included abandoning military conscription and speeding up Germany's exit from nuclear power.

In Germany, same-sex couples have been able to register civil partnerships that legally fall short of formal marriage since 2001. Heterosexual married couples can, unlike same-sex couples, reduce their tax burden by filing joint income tax returns, thus paying less than single taxpayers.

The partnerships were introduced by a previous center-left government. While Merkel's party accepts them, many conservatives remain reluctant to go further; and Germany's constitution states that "marriage and the family shall enjoy the special protection of the state."

On Tuesday, 13 Christian Democrats issued a joint statement saying that the move would be "only consistent" with the fact that gay partners have the same responsibilities toward each other as married spouses. They said they will seek fellow conservatives' backing after Parliament returns next month from its summer recess.

They won support from Merkel's minister for families, Kristina Schroeder. The call comes "at the right time" and same-sex couples in civil partnerships "take on long-term responsibility for each other, so they live out conservative values," Schroeder, a Christian Democrat, was quoted as telling the daily Sueddeutsche Zeitung on Tuesday.

Germany's highest court earlier this month ruled that a civil servant in a same-sex partnership was wrongly denied a wage supplement granted to married colleagues, and the court is currently considering complaints against the difference in income tax rules.

The conservative lawmakers who are calling for a change said it was "not acceptable that policymakers repeatedly ... have to be ordered by the Federal Constitutional Court to abolish this unequal treatment."

Their call was welcomed by opposition parties and by the Free Democrats, the junior partners in Merkel's center-right coalition, who have long called for a change.

But it may be a tough sell to some of their own colleagues — not least in the Christian Social Union, the socially conservative Bavarian sister party to Merkel's Christian Democrats.

Gerda Hasselfeldt, the head of the CSU's parliamentary group in Berlin, told news agency dapd she was "extremely skeptical" about granting same-sex couples equal tax treatment.

"Marriage between a man and a woman has special protection because it is fundamentally directed at the propagation of life," Hasselfeldt said. "That is not the case in homosexual relationships."