Chancellor Angela Merkel's coalition faces a further loss of support if her Free Democrat partners insist on pursuing a battle over the leadership of party chairman and Foreign Minister Guido Westerwelle.
Dirk Niebel, development minister and a member of the FDP's executive board, said on Saturday that Westerwelle's party rivals were damaging the FDP and that their campaign could further erode support for the party.
Westerwelle has rejected calls to resign as FDP leader, saying he would not abandon ship in stormy weather.
Westerwelle, 48, is deeply unpopular in Germany because of his ineffective leadership, abrasive style and a view that he has catered to special interests. The pro-business party promised tax cuts in the 2009 campaign but failed to deliver.
The FDP's steep fall in opinion polls has been one of the main reasons Merkel's government has fallen far behind the centre-left opposition bloc and has caused tension in her three-way coalition.
"What will be accomplished if we can't try to bounce back with Guido Westerwelle?" Niebel said in an interview with Focus magazine before a party meeting in Stuttgart starting on Tuesday, where rebels are expected to push to dump Westerwelle.
"It would leave us with a crippled chairman all the way to the May party congress, and a battle over his successor," said Niebel, a Westerwelle ally in the FDP. An FDP leadership fight would eclipse the party's efforts to rebuild its standing in Merkel's coalition, he said. The FDP faces heavy defeats in a series of seven state elections this year and regional leaders have urged Westerwelle to step aside.
"I'll do all I can so that Westerwelle stays in office as long as possible," Niebel said. "Obviously many opponents are now out to settle some old scores ... It's like a schoolyard fist fight ... Some are out there kicking people when they're down."