Martin Schulz with Hungary's Prime Minister Viktor Orbán in 2012 | Thierry Charlier/AFP via Getty Images Martin Schulz to Viktor Orbán: No refugees means no subsidies ‘We won’t accept that solidarity as a principle is questioned,’ German Social Democrat leader says.

BERLIN — German Social Democrat leader Martin Schulz said that, if elected chancellor, he would push for the EU to cut subsidies to countries that do not take in refugees.

“With me as chancellor ... we won’t accept that solidarity as a principle is questioned,” Schulz said on Tuesday at a conference of a business lobbying group with ties to his party.

Schulz, the Social Democrats' (SPD) candidate for chancellor in September's parliamentary election, said the influx of refugees into the Continent in recent years was “not a German problem, but a European challenge.”

His comments came as the European Commission voted to launch infringement proceedings against the Czech Republic, Poland, and Hungary for not taking in refugees under a mandatory 2015 quota system advocated by Germany that aims to relocate 160,000 refugees across the Continent.

East European leaders, particularly Hungarian Prime Minister Viktor Orbán, have repeatedly railed against the EU resettlement plan.

On Monday, Orbán told the Hungarian parliament that his country "will not give in to blackmail from Brussels and we reject the mandatory relocation quota.” Schulz shot back swiftly at Orbán in his speech on Tuesday.

“Mr. Orbán says 'That's a German problem,'" Schulz said. "Let me make this perfectly clear: When it comes to agricultural policy, it's all 'Yes, please.' When it comes to subsidies, it's all 'Yes, please.' And when it comes to solidarity in refugee policy, it's 'No, thank you' — that's not acceptable."

Poland and Hungary are among the largest net recipients of EU funds, while Germany is a net contributor to the bloc.

The Social Democrats enjoyed a bounce in the polls after Schulz was chosen as their candidate for the chancellorship earlier this year. But support for the SPD has since fallen back to 24 percent — 14 percentage points behind Chancellor Angela Merkel’s conservatives, according to the most recent Forsa poll. Just three months ago, the parties were neck-and-neck.