Martin Schulz, chancellor candidate of the German Social Democrats (SPD) | Steffi Loos/Getty Images Martin Schulz says no death penalty vote for Turks in Germany Voting on a law that contradicts German values should not be allowed, Social Democrat leader says.

Turks living in Germany should be barred from voting on the reintroduction of the death penalty in Turkey, Social Democrat leader Martin Schulz said.

Schulz, his party's candidate to become chancellor in September's general election, told Der Spiegel in an interview published Friday that if the Turkish government were to carry out a referendum on the death penalty, "it must be clear that such a vote cannot take place among the Turks living in Germany."

"We cannot allow a vote in Germany on a law that contradicts our values and our constitution," Schulz said, echoing remarks by Foreign Minister Sigmar Gabriel earlier this week.

Government spokesman Steffen Seibert said Friday it would be “political unimaginable” to allow such a vote for Turkish people living in Germany.

Turks living abroad — including around 1.4 million in Germany — were eligible to vote in last month's referendum on constitutional changes.

President Recep Tayyip Erdoğan has suggested he could call a referendum on the reintroduction of the death penalty if the national parliament rejects a proposal to bring it back.

Erdoğan in March said he expects the Turkish parliament to back the plan. He has been campaigning to restore capital punishment since a failed military coup in July last year. The death penalty was abolished in 2004 as part of Turkey's bid to join the European Union.