Friedrich Merz, a candidate to replace Chancellor Angela Merkel as leader of the Christian Democratic Union (CDU), has questioned whether Germany can continue with its asylum policy.

Mr Merz, a long-time critic of current Chancellor Merkel, spoke of Germany’s asylum laws on Wednesday at a regional conference of the CDU that took place in Seebach in the region of Thuringia, Kronen Zeitung .

“I have long believed that we must be prepared to talk openly about this asylum fundamental right, whether it can continue in this form if we seriously want a European immigration and refugee policy,” Merz said.

Germany is unique in that the right to claim asylum is its the country’s constitution.

Merz also added that he did not support the idea of accepting climate change as a legitimate argument for asylum saying that he would demand further clarification regarding that definition in the proposed UN Migration Pact, but noted that legitimate political asylum was not comparable to the effects climate change.

“These are things that we can not accept in Germany through the back door,” he said.

One of Merz’s main rivals, Health Minister Jens Spahn, who is also a critic of Chancellor Merkel’s migrant policy, said that German basic asylum law is not the real problem. “At the core, that’s not the big challenge in migration,” he told German media on Thursday, adding: “the real issue is how to secure the EU external border.”

The UN Migration Pact has also been heavily criticised by Spahn, who earlier this month  that “It is important that Germany retains its sovereignty to control and limit migration.”

Chancellor Merkel, meanwhile, has vehemently  the pact, saying it was a “win-win” agreement for Germany and adding that opponents of the pact were, “people who say they can solve everything themselves and don’t have to think about anyone else — that is nationalism in its purest form.”