A flood of senior German politicians visiting the UK this week have been left confused and unnerved by the hardline rhetoric set out by Boris Johnson on trade talks, prompting warnings that the risk of a breakdown, or a no-deal Brexit, is as high as it has ever been.

Germany takes on the EU presidency in the second half of this year, and will have a crucial role in helping the European commission to steer the talks on a future UK-EU trading relationship to a successful conclusion by the end of the transition period in December.

There has been a consensus across German politics about the need to reach the closest possible relationship with Britain after Brexit. Senior German politicians have even been drafting a series of partnership offers to the UK on security, defence and foreign affairs, possibly wrapped up in a new Anglo-German friendship treaty.

But the hardline tone of Johnson’s recent speeches has thrown the German political class visiting London for a week-long symposium at the London School of Economics. The former trade minister Greg Hands was forced to reassure his German interlocutors that the British people did not want to set up a “Singapore-on-Thames”, and nor did Johnson.

But Ralph Brinkhaus, the parliamentary leader of Angela Merkel’s Christian Democratic Union party, said: “Within the next 11 months we have to decide what the common base of the relationship will be with the UK. We will compete. No question about that and no one is afraid of that. But we can have competition with cooperation or competition with conflict. Listening to the government’s speeches this week, I am not quite sure what the position is of the UK.”

Robert Habeck, the leader of the German Greens, and a potential German chancellor after next year’s elections, was also gloomy that a deal could be struck. He said: “Johnson has stated that under no circumstances does he intend to conduct the negotiations after 11 months. He has categorically ruled out extension of the negotiations. He does not want to accept the EU rules for work, environment, or the jurisdiction of the European court of justice. The EU, on the other hand, cannot accept tax or regulatory dumping on its doorstep and must protect its single market and insist on a level playing field. The risk of an unregulated no-deal Brexit is still high, and maybe has never before been higher.”

The anxiety was shared by Norbert Röttgen, the chair of the Bundestag foreign affairs committee and a member of Merkel’s party. “The question is whether we are listening to policy or rhetoric aimed at a domestic audience,” he said. “There is a danger on both sides that the intense rhetoric about principles gets emphasised time and again and so creates a reality of its own. The risk is that it gets difficult to switch to a different pragmatic response by the end of the year because that would mean losing face.”

He suggested the scale of the negotiations, and the apparent differences between the two sides on issues such as regulatory alignment and the European court of justice, meant a full deal would be unachievable by the end of the year. “The rhetoric will continue through the summer on both sides, but the people that are working on the technical stuff will try to do their job.” He said an initial deal might be reached by November “covering security, and those trade areas that are vital to limit mutual damage”. But he predicted that such a deal would have leave out a significant proportion of trade that would then have to be negotiated further on a sectoral basis in a process freed of artificial time limits.

The choice for both sides, he said, was between mutual self-harm and a cooperative relationship.

Asked in March 2016 how Germany would react if Britain left the EU, Wolfgang Schäuble, the current Bundestag president, said: “We will cry.” The tears have been shed, but the angst remains.