(Adds criticism from Merkel's right)
By Holger Hansen and Michelle Martin
BERLIN, March 9 (Reuters) - Germany's Social Democrats on Friday named two seasoned pro-European politicians to key posts in a new government, with Hamburg Mayor Olaf Scholz to become finance minister in Europe's largest economy and Heiko Maas becoming foreign minister.
The SPD's designated leader Andrea Nahles and Scholz announced the party's six ministry appointments at a news conference. Maas, who was justice minister, will replace Sigmar Gabriel as foreign minister, Nahles said.
The SPD on Sunday said two-thirds of its members had voted in favour of a repeat of the 'grand coalition' with Chancellor Angela Merkel's conservatives that has governed Germany since 2013. The new government will be sworn in on March 14.
Nahles said Scholz, 59, a lawyer who backs closer European integration, would also be vice chancellor in the government, underpinned by a coalition deal which incorporates SPD-inspired commitments to deepening cooperation in the European Union.
Merkel's conservatives are upset that she agreed to give the SPD the finance post to secure the coalition deal after eight years under budget hawk Wolfgang Schaeuble, who was known for his insistence on austerity for indebted euro zone states.
The SPD generally favours more spending than the conservatives but the parties have agreed to stick to the goal of a balanced budget with no new debt.
But Jens Spahn, a Merkel critic who since his appointment as health minister-designate has been seen as the leader of her bloc's arch-conservative wing, warned in a newspaper interview that he would resist deeper integration.
"The creeping self-empowerment driven by institutional self-interest has to stop," he told the newspaper Die Welt, rejecting proposals for a finance minister for the euro zone.
On Tuesday, a senior conservative warned the SPD they would jeopardize the hard-fought coalition pact if they went overboard with spending plans for Europe.
Maas, 51, is best known for introducing laws in his previous job that forced social media companies such as Facebook and Twitter to remove hate speech from their sites.
He is an outspoken critic of the far-right Alternative for Germany (AfD), racist crime and anti-Semitism.
Maas plans to visit key foreign capitals, including Paris - possibly as early as next week - London, Warsaw, Brussels and Washington.
Hubertus Heil will take over as labour minister. The 45-year-old has been a member of the Bundestag lower house for almost 20 years and organised two national election campaigns for the SPD as its general secretary.
The post puts him at the helm of the ministry with the biggest budget - some 135 billion euros. The SPD won labour reforms in the coalition talks such as enabling workers to switch to shortened hours for limited periods.
Katarina Barley, 49, who took over as family minister last year, will head the justice ministry. Born to a British father and German mother, she studied law and once worked at the Federal Constitutional Court.
Franziska Giffey, 39, from the former Communist East, will become family minister. Until now she has been mayor of the Berlin district of Neukoelln, home to many immigrants and high unemployment.
Svenja Schulze, a 49-year-old who worked as research and science minister in the western state of North Rhine-Westphalia until the SPD lost the regional election there in 2017, was chosen as environment minister. (Reporting by Michelle Martin; additional reporting by Andrea Shalal and Thomas Escritt; Editing by Janet Lawrence, Larry King)