BERLIN (Reuters) - German Finance Minister Wolfgang Schaeuble has proposed the introduction of a special tax on gasoline in European Union member states to finance refugee-related costs such as strengthening the continent’s joint external borders.

An EU sign is seen as migrants wait in the no man's land to cross the border to Slovenia from Trnovec, Croatia, October 19, 2015. REUTERS/Srdjan Zivulovic

Schaeuble’s proposal drew criticism from members of his own conservative party, the Christian Democratic Union (CDU), as well as from the Social Democrats (SPD), junior partner in Chancellor Angela Merkel’s ruling coalition.

“I’ve said if the funds in the national budgets and the European budget are not sufficient, then let us agree for instance on collecting a levy on every liter of gasoline at a specific amount,” Schaeuble told Sueddeutsche Zeitung newspaper in an interview published on Saturday.

“We have to secure Schengen’s external borders now. The solution of these problems must not founder due to a limitation of funds,” the veteran politician said.

Asked if all EU countries should increase their payments to Brussels to finance joint refugee-related costs, Schaeuble said: “If someone is not willing to pay, I’m nonetheless prepared to do it. Then we’ll build a coalition of the willing.”

Schaeuble gave no details on how high the extra levy on gasoline should be and whether Brussels or the EU member states would be in charge of collecting it.

A finance ministry spokesman declined to comment.

Schaeuble’s was met with criticism across the party political spectrum.

“I’m strictly against any tax increase in light of the good budgetary situation,” said CDU deputy Julia Kloeckner who wants to win a regional election in the western state of Rhineland-Palatinate in March.

Germany achieved a larger-than-expected budget surplus of 12.1 billion euros ($13.20 billion) in 2015 and will use the windfall to pay for accommodating and integrating refugees.

“We Social Democrats want to hold society together instead of dividing it with a new refugee toll à la Schaeuble,” SPD deputy Ralf Stegner told Reuters.

Earlier on Saturday, Bavarian state premier Horst Seehofer threatened to take Merkel’s government to court over its “open doors” refugee policy as political pressure grows for the chancellor to reduce the number of new arrivals.