Germany's Green party is calling for the unprecedented appointment of two vice chancellors for their participation in a three-way coalition, adding another hurdle to forming a government.

Chancellor Angela Merkel's Christian Democrats (CDU), Greens and liberal Free Democrats (FDP) are in exploratory talks to form a "Jamaica" coalition, so named for the colors of the three parties.

But negotiations to form a three-way coalition could leave Germany without a government for months, as each of the junior parties puts forward its wishes and demands to make its mark on policy.

Read more: Merkel's coalition talks for next German government — What you need to know

Against Basic Law?

"Greens and the FDP must equally help coordinate the government's work," Michael Kellner, a Green party official, told the Monday edition of the Bild newspaper.

"In such a possible coalition, the coordination of government work cannot only be in the chancellery and with another partner," he said. "Rather, it must lie with all three: the CDU, Greens and FDP."

The Greens won 8.9 percent of the vote in September's national election, compared to the FDP's 10.7 percent. That would give the pro-business party dibs on the vice chancellor position.

The latest demand from the Greens may go against Article 69 of Germany's Basic Law, which states: "The chancellor appoints a federal minister to be his/her deputy."

However, the rules of procedure allow for a previously named minister to preside over the Cabinet in the event both the chancellor and vice chancellor are absent, or incapacitated.

cw/cmk (AFP, dpa)