Christian von Stetten, a member of Merkel's conservative Christian Democrats (CDU), said on Saturday members of parliament — and not those negotiating the coalition — would have the final say on a deal.
"The coalition agreement is not the bible,” von Stetten, who chairs the Small and Medium-size Business Association of the CDU party in parliament, told the German daily newspaper Augsburger Allgemeine.
A significant number of Merkel's conservatives are dismayed that the SPD, which saw its support plummet to 20.5 percent at the last general election in September, claimed six ministries in the coalition deal, including the powerful Finance Ministry. The CDU garnered 32.9 percent of the vote.
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The conservative-leaning mass-circulation daily newspaper Bild has accused Merkel of "gifting” the government to the center-left SPD.
Von Stetten, who has claimed the distribution of Cabinet posts is a "political mistake,” said it was the job of lawmakers to hold the party leadership to account.
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"As the parliamentary group for medium-sized business, we can make sure that those things that were well-intentioned — but not carefully thought through — can be held up and corrected," von Stetten said.
Part of von Stetten's reasoning was that the coalition parties had only a slender majority, giving smaller groups more clout in chamber votes.
The Small and Medium-size Business Association of the CDU boasts a majority of conservatives in the Bundestag among its members. Von Stetten has said he would have preferred a conservative-led minority government to the Grand Coalition deal that was agreed.
Merkel, who will serve her fourth chancellorship if the coalition deal can hold, has also been criticized by the CDU's youth wing for making too many concessions.
rc/jlw (AFP, AP, dpa, Reuters)