Following Chancellor Angela Merkel's decision to row back on her conservative party's opposition to gay marriage, her opponent in September's elections said on Tuesday that his party would push for a parliamentary vote on the issue.

Social Democratic (SPD) chancellor candidate Martin Schulz did not say when his party would present a draft law on marriage equality to the Bundestag. However, this is the last week of the current parliamentary session.

Schulz said he hoped Merkel's Christian Democrats (CDU) and her sister party, the Bavarian-based Christian Social Union (CSU), would cooperate on drafting the law, but, if not, the SPD would forge ahead and discuss the next steps at a meeting on Tuesday afternoon.

The CDU and CSU have repeatedly blocked efforts to introduce full marriage equality for same-sex couples in Germany despite overwhelming public support for the move.

Same-sex couples are currently able to register civil partnerships in Germany.

Merkel said on Monday she was hoping for a discussion on marriage equality that would be conducted with dignity, and called it "a question of conscience."

Following Merkel's comments, lawmakers from the SPD, who are in coalition with the CDU and CSU, and from the opposition Greens and The Left (Die Linke) demanded a vote take place this week.

If the vote were conducted without party pressure, it is expected that a marriage equality law would easily be passed.

But it was still unclear if a vote will actually take place this week. "There is no need for a rushed decision," Michael Grosse-Broemer, who leads the CDU/CSU group in the Bundestag, said on Tuesday.