BERLIN (Reuters) - The head of Angela Merkel's Bavarian allies has attacked a plan by the opposition Social Democrats (SPD) to put any decision on forming a "grand coalition" with her to a vote of its grassroots members, warning against tactics that threaten stability.
The SPD agreed late on Friday it would poll its 472,000 members if it decides to join Merkel - a union many in the party oppose for fear they will lose their political identity alongside the highly popular chancellor.
The poll could turn into an unwieldy process that complicates the creation of a new government. It carries huge risks for the SPD leadership should the grassroots reject any tie-up, and puts Merkel under pressure to make concessions to her rivals to win their support - such as granting them the position of finance minister in her new cabinet.
Bavaria State Premier Horst Seehofer said Germans had voted for a government led by Merkel, and to torpedo attempts to create a coalition on tactical grounds would damage the SPD.
"The heads of the parties all have a mandate and the responsibility to ensure stability," Seehofer said, in an interview with newspaper Bild am Sonntag, to appear on Sunday.
"We are not a bunch of rabbits, running round a field because we are too scared to form a government."
A new government must emerge within the next two months, he said, or Germany risked making itself look ridiculous.
Merkel's Christian Democrats emerged as the dominant party from Sunday's election but her party fell short of a majority, winning 311 seats in the 630-seat parliament while the SPD took 192. The Greens got 63 seats and the radical Left party have 64.
Her conservatives need a new coalition partner and would prefer a grand coalition with the SPD, a reprisal of the right-center alliance that Merkel led from 2005 to 2009. Alternatively she could look to the Greens.
In an extraordinary meeting on Friday 200 SPD leaders gave embattled chairman Sigmar Gabriel a green light to begin exploratory talks with the conservatives which could start on Monday to see if there is scope for full-fledged talks. Based on past experience full-fledged talks would take up to two months.
Hermann Groehe, general secretary for the CDU welcomed the SPD's agreement to hold exploratory talks.
"We must consider together whether the CDU and SPD can create a stable foundation for the next four years. We will enter the talks with our election program, and with a clear mandate from the electorate," he said.
The Greens on Saturday also said they would be open to holding exploratory talks with Merkel's conservatives, as well as with the SPD and the Left party.
An opinion poll on Friday showed two-thirds of SPD members oppose a grand coalition because they fear the party could wither further in Merkel's shadow.
The right-left coalition would nevertheless be the most popular constellation in Germany, the poll also found. More than half of Germans said they would welcome a grand coalition.
Merkel had wanted to continue in power with her outgoing coalition partner, the business-friendly Free Democrats (FDP), but they failed to clear the 5 percent threshold to enter the Bundestag lower house of parliament.
(Reporting by Alexandra Hudson; editing by David Evans)