FILE PHOTO: Andrea Nahles, leader of Social Democratic Party (SPD), speaks during a budget debate at the lower house of parliament Bundestag in Berlin, Germany, July 4, 2018. REUTERS/Hannibal Hanschke/File Photo

BERLIN (Reuters) - German Social Democrat leader Andrea Nahles questioned her party’s future in the government after a rocky six months during which the coalition has twice come close to collapse.

In an interview with Die Zeit newspaper, Nahles blamed divisions within the two conservative parties in Chancellor Angela Merkel’s grand coalition, which relies on the center-left Social Democrats (SPD) to govern.

“If the internal spat among the conservatives continues to overshadow everything, there obviously comes a point at which good substantive work no longer makes any sense,” Nahles said in the interview, extracts of which Die Zeit released before publication on Thursday.

The coalition - made up of Merkel’s Christian Democrats (CDU), their Bavarian CSU allies and the SPD - had a row last month over the fate of the security service chief. That followed a dispute between the CDU and CSU in the summer over immigration. They ultimately found compromises on both issues.

“Ever since this government has taken up work or actually ever since the coalition negotiations started, the dispute among conservatives over what direction to take has been a huge burden for this coalition,” Nahles said.

The SPD was reluctant to form another grand coalition with the conservatives after a national election in September 2017 but initial talks between the conservatives and two smaller parties failed, leaving no other viable government.

The government took office only in March, nearly six months after the election, and the coalition deal includes a clause that envisages a review of its progress after two years. This is widely seen as giving the SPD an exit should it want one.

Nahles also criticized Merkel, saying the chancellor had not yet been able to steer the coalition into calmer waters.

Differences over how to tackle the problem of diesel cars with excessive emissions have also strained the government, though the parties agreed last week to ask carmakers to offer owners trade-in incentives and hardware fixes.