Polish PM to decide on justice minister fate on Monday-spokesman

* PM Tusk may dismiss justice min Gowin from government

* Gowin leads group of conservative MPs in Civic Platform

* Gowin unlikely to leave party, undermine govt - source

WARSAW, Feb 28 (Reuters) - Polish Prime Minister Donald Tusk will decide on Monday whether to dismiss Justice Minister Jaroslaw Gowin, a spokesman said on Thursday, bringing to a head a long-standing feud that threatens to destabilise the ruling coalition's majority in parliament.

Tusk has been at odds with the more conservative Gowin over a string of social issues such as in-vitro fertilisation.

Gowin also clashed recently with the more socially liberal Tusk when Gowin opposed the party's bill that would have given limited legal rights to homosexual couples in staunchly Catholic Poland.

"Prime Minister Tusk has informed the board of Civic Platform that he would take the decision regarding the presence of minister Gowin in the government on Monday," government spokesman Pawel Gras wrote on Twitter.

Gowin has an informal group of several conservative followers among the 206 deputies of the centre-right Civic Platform (PO) party.

If Gowin is dismissed from the coalition and decides then to leave the party, it could potentially cost the ruling coalition of Civic Platform and the Peasants' Party its majority, although party figures said such a scenario was unlikely.

The coalition holds a 5-seat majority in the 460-member lower chamber of parliament, the Sejm.

Poland, the largest central European economy, has been a symbol of political stability in recent years in a region where the global economic slump has already toppled governments in Romania and most recently in Bulgaria.

The feud between Tusk, who is PO leader, and Gowin has underlined tensions within the ruling party as well as within Polish society, where younger Poles seeking a more secular society clash with a deeply religious older generation.

But other party figures doubted Tusk would allow the differences to cost him a majority in Parliament or force an early election.

"This is an ultimatum for Gowin," said Lena Kolarska-Bobinska, an member of the European Parliament from Civic Platform. "Gowin has time until Monday to agree to the leadership of Tusk."

"I am convinced that Tusk will not risk losing the majority in the Sejm or having an early election ... Tusk probably eyes a few MPs from other parties that would like to join PO," said Kolarska-Bobinska.

A party executive told Reuters that even if Gowin were dismissed from the government, he was likely to opt to stay within the party.

"I do not know what the decision (on Gowin) will be, negative or positive. Even if it is negative, I think that nobody will leave PO MPs club or the party," Marzena Okla-Drewnowicz, a PO party executive told Reuters.

Gras also quoted Tusk as saying he would run for reelection as the leader of Civic Platform next year.

Gowin, who was unavailable for comment, replied on Twitter to Gras: "I don't like Monday's" and pasted in a link to the song that has the same title. (Reporting by Marcin Goettig and Pawel Sobczak; Writing by Marcin Goettig; Editing by Roger Atwood)