BERLIN (Reuters) - German Chancellor Angela Merkel will promote one of the most prominent critics from within her conservative party, Jens Spahn, to the cabinet, handing him the post of health minister, Bild am Sonntag newspaper reported on Sunday.

Chancellor Angela Merkel talks to Jens Spahn during debate at the German lower house of parliament Bundestag in Berlin, Germany, February 22, 2018. REUTERS/Axel Schmidt

Merkel, hoping to clinch a “grand coalition” with the Social Democrats (SPD) to secure her fourth term, is due to announce her choice of six cabinet ministers from her own Christian Democrats (CDU) on Sunday.

Putting Spahn, who sharply criticized Merkel’s open-door migrant policy and is seen as a champion of the party’s right wing, in the cabinet is a sign that Merkel is keen to assuage her critics who have called for new blood and a fresh direction.

The 37-year old has been a deputy finance minister.

Citing party sources, Bild am Sonntag also reported Merkel has, as expected, decided to put long-standing ally Peter Altmaier in charge of the economy ministry, responsible for expanding broadband across the country.

The paper also said Ursula von der Leyen, once tipped as a possible successor to Merkel, would remain defense minister. It also reported that senior CDU figure Julia Kloeckner will take over as agriculture minister.

Reuters was not able to confirm or deny the report.

After 12 years as chancellor and about 18 years as CDU chief, Merkel’s authority is starting to wane.

Her conservative bloc, which includes Bavaria’s Christian Social Union (CSU), scored their worst result since 1949 in a September election after bleeding support to the far-right Alternative for Germany (AfD).

In a further blow, she failed to agree on a coalition deal with two smaller parties, forcing her to turn to the Social Democrats with whom she had shared power from 2013 to 2017.

A reluctant partner, having seen support fall to its lowest since World War Two, the SPD agreed on a deal which party members have to vote on. The result of the postal ballot is due on March 4 and is unclear.

If members vote “no” to the deal, the most likely outcome is a new election or possibly a minority government.

In response to growing rumblings in her party about her future, Merkel has promised “renewal”.

She took a big step to grooming a successor last week by nominating ally Annegret Kramp-Karrenbauer, premier of the tiny western Saarland state, to take over as CDU general secretary.

CDU members meet on Monday and are expected to approve the coalition deal and also Kramp-Karrenbauer in her post.

The SPD and CSU are to announce their cabinet picks at a later date.