Germany’s vice-chancellor and economy minister put Berlin on a collision course with Brussels by warning that imposing anti-dumping duties on solar panels from China would be a “grave mistake”.

Philipp Rösler’s statement came as Germany’s leading manufacturing industry organisation also called for urgent negotiations with China to head off the threatened import duties, which are expected to be announced formally by the European Commission in early June.

The flurry of German anxiety comes a week before a visit by Li Keqiang, China’s new premier, who is due to meet Angela Merkel, the German chancellor, in Berlin next Sunday. Germany is the only EU member state he will visit on his first foreign tour.

The comments risk undermining Karel De Gucht, the trade commissioner, as he faces off against Beijing in the EU’s largest ever trade case, based on the €21bn of solar products China exported to Europe in 2011.

Mr De Gucht has recommended that such products face duties averaging 47 per cent after concluding that Chinese manufacturers illegally dumped their products, or sold them below cost, in Europe.

In addition to the solar case, the commissioner is also grappling with Beijing over a highly-contentious probe into China’s telecommunications network equipment suppliers, Huawei Technologies and ZTE Corp.

After more than a year of sabre-rattling, Mr De Gucht last week won backing from the commission to open an anti-dumping and anti-subsidy investigation into the sector and has warned that he will do so shortly if Beijing does not offer concessions.

Under EU rules, Mr De Gucht can press both cases without member states’ support – although his ability to do so would be weakened. In an effort to thwart him, Beijing has repeatedly lobbied national governments to oppose the investigations. As the EU’s biggest economy and biggest exporter to China, Germany has been a particular focus.

Mr Rösler’s portfolio includes external trade and his intervention reflects Berlin’s position that Europe and China must find a consensual way of dealing with the solar panel dispute.

In an interview with the Welt am Sonntag newspa per, Mr Rösler said that “punitive duties are the wrong instrument” to deal with the dispute. “German industry is quite rightly very concerned” about the threatened action, he said, and its potential for retaliatory action by China affecting German exports.

“I expect the commission to do everything to prevent an all-out trade conflict,” he said. “The Commission must aim for a negotiated solution and dialogue, instead of threats.”

In a separate statement, Ulrich Grillo, president of the BDI, the German manufacturers’ association, said that every possibility for negotiation must be exhausted before any action was taken to impose duties.

“Punitive tariffs damage both sides,” he said. “We urge the government to put pressure on the commission.”

Ms Merkel irritated trade officials in Brussels last August when, on a visit to Beijing, she publicly suggested the solar dispute should be solved through dialogue – an intervention that some observers believe may have stiffened Mr De Gucht’s resolve.

The chancellor’s comments were unusual since the solar case was spearheaded by a German photovoltaic manufacturer, SolarWorld. Still, it has been contested by WackerChemie, a German chemicals company that is Europe’s biggest supplier of polysilicon, the basic ingredient in solar panels, as well as a legion of smaller EU firms that install panels on roofs and buildings.

They have argued that more expensive panels would damage an industry already struggling in Europe as governments curb subsidies. A study commissioned by a group known as the Alliance of Affordable Solar Energy claimed that more than 242,000 jobs would be put at risk in Europe if punitive tariffs were imposed.

The commission’s own review, seen by the Financial Times, heaped doubt on those figures, predicting the negative impact would be far more limited.