Legal experts at Germany's lower house of Parliament have serious doubts about the legality of introducing a cap on refugee numbers, according to a document obtained by German broadcaster ARD.

German Chancellor Angela Merkel's Christian Democratic Union (CDU) and their Bavarian allies, the Christian Social Union (CSU), have been embroiled in a dispute over the idea for weeks.

Merkel has resisted calls by some members of her party for an "Obergrenze," or cap on the number of refugees entering Germany, and has said that the right to asylum for people suffering from political persecution cannot be limited.

But Horst Seehofer, leader of the CSU which governs the federal state of Bavaria where many refugees head, has called for limits to be placed on migrant inflows.

Legal experts at Germany's Bundestag lower house, who provide independent views, found that EU asylum and refugee laws did not provide for any numerical limit being placed on people seeking protection, the report said.

They said that on this issue EU legal guidelines generally override national laws.

A European-wide cap on the number of refugees would be "problematic" and would only be imaginable if the people granted refugee status under the Geneva Convention were sent to safe third countries upon being rejected, ARD said, citing the report.

But the legal experts said it was "extremely doubtful" whether deporting and rejecting refugees could be justified by saying a cap would otherwise be exceeded, ARD said.

(Reporting by Michelle Martin; Editing by Ruth Pitchford)