BERLIN (Reuters) - The general secretary of Chancellor Angela Merkel’s conservatives called on Thursday for an end to internal party divisions that have stressed her Christian Democratic Union (CDU).

Annegret Kramp-Karrenbauer gives a statement during a Christian Democratic Union (CDU) leadership meeting in Berlin, Germany July 1, 2018. REUTERS/Hannibal Hanschke

Annegret Kramp-Karrenbauer, a member of the more centrist wing of the CDU and possible successor to Merkel, told the mass-circulation daily Bild that the party was founded to encompass a range of views and this should remain the case today.

The party’s unity has been challenged increasingly by more hardline members, including another possible Merkel successor, Health Minister Jens Spahn.

The conservative bloc has been strained over migration policy since the chancellor’s decision in 2015 to open German borders to more than a million refugees fleeing war and poverty in the Middle East, Africa and central Asia.

Some CDU members have allied themselves with Interior Minister Horst Seehofer and his CSU, the CDU’s Bavarian sister party, particularly on migration and euro zone reforms.

Seehofer’s demands for stricter migration policies nearly brought down Merkel’s coalition government earlier this month.

“Listening to some of the statements of the last days, I wish there had been more focus on the joint political goals,” Kramp-Karrenbauer said.

“What is absolutely not acceptable is the tone in which these debates have been conducted,” she told the paper. “No one at the grassroots understands that. It’s completely undignified.”

Bild said the party had 420,240 members at the end of June, and it had added a net 1,000 in 2017, the first increase since 2003.

Merkel, 64, vowed last week to stay in office despite what she called “demanding times” at home and abroad. She criticized what she called the harsh tone of domestic debate, but denied that her authority had been damaged.