Michel Barnier has said Brexit is at a standstill after the crushing rejection of Theresa May’s deal by MPs but offered to return to the negotiating table if parliament forces Theresa May to shift her “red lines”.

The motivations of the MPs who delivered the rebuff – a defeat by 230 votes, the largest ever for a sitting government – were described by the EU’s chief negotiator as “contradictory”.

Barnier said parliament had failed to offer an alternative vision on Tuesday evening, warning May that nothing could progress until she found a Commons majority for a deal.

His comments were echoed by the German chancellor, Angela Merkel, who said there was still time to negotiate, but “we believe it is up to the British side, as the prime minister has announced, to tell us what happens next.”

Barnier told the European parliament in Strasbourg that statements from MPs during the Commons debate had “made us sad”. He added: “Objectively speaking, this vote is not a clear manifestation of a positive majority which would define an alternative project, and an alternative to the proposal on the table today,” Barnier said.

“So, in this context, it is up to the British authorities today or tomorrow to assess the outcome of this vote and up to the British government to find how we are to take things forward on 29 March towards an orderly withdrawal.”

EU states escalate no-deal preparations after May defeat Read more

Barnier, whose speech was applauded by MEPs despite the problems being faced in ratifying the deal he brokered, told the parliament: “Now, with this standstill, until we have found a way forward which will see a full majority we won’t be able to move forward, so this is why the future steps must be indicated very clearly … by the British government.

He added: “I would like to remind you that your parliament, and unanimously the European council, have always said that if the UK chooses to shift its red lines in the future, and it makes that choice, a choice to be ambitious, and go beyond a simple free trade agreement, which would be quite something, then the European Union will be immediately ready to go hand in hand with that development and to give a favourable response.”

The former French minister said that whatever emerged from future talks, the withdrawal agreement would still need to contain the contentious Irish backstop for avoiding a hard border, which Brexiters fear will trap the UK in a customs union.

Critics of May’s deal have called for a time limit or unilateral right to exit the arrangements.

While declining to speculate on the different scenarios now opening up in the negotiations, Barnier told MEPs: “The backstop that we agreed with the UK must remain a backstop, must remain a credible backstop. The backstop must remain a backstop.”

With only 10 weeks to go until 29 March, when the UK is due to leave the EU, Barnier said the risk of a no-deal Brexit was greater than ever and the European commission was “stepping up” its preparations.

Brussels is waiting on the UK parliament to take control of the Brexit talks next Monday, when the prime minister will put forward a motion detailing her plans, which will be liable to be amended by MPs.

The first expected step is for MPs to seek an extension of the two-year negotiating period.

Peter Altmaier, Germany’s economics minister, who is close to Angela Merkel, suggested a request would be endorsed by the 27 member states.

He said: “When parliament needs more time, then this is something that will have to be considered by the European council, and personally I would see that as a reasonable request.”

Facebook Twitter Pinterest France’s EU affairs minister, Nathalie Loiseau, said the withdrawal text cannot be reopened. Photograph: François Guillot/AFP/Getty Images

Asked about delaying Brexit, France’s EU affairs minister, Nathalie Loiseau, nodded, however, to Emmanuel Macron’s concerns about such a prolongation.

“It’s a hypothesis … juridically and hypothetically it’s possible but Theresa May has not asked and it needs the agreement of the other 27 European nations,” she said. “But to do what? If it’s to say we want more European concessions … no.”

Loiseau also hinted that Barnier was offering only to rethink the political declaration on the future relationship, which is legally non-binding, rather than the withdrawal agreement containing the backstop.

She said: “The text cannot be reopened, especially after we’ve gone 17 months with all the coming and going. It’s been one-third of my work since I became minister, which is a bit excessive, and we have other things to do in Europe than busy ourselves with a divorce.”

Germany’s foreign minister, Heiko Maas, said the ball was in Britain’s court to bring clarity to the chaos.

“The MPs of the lower house have not made it known what they want, only what they don’t want,” he told the broadcaster Deutschlandfunk on Wednesday morning. “That is not enough.”

He added he did not support the idea of renegotiating the deal, saying that many compromises had already been made by both sides. “If one had been able to offer more, we would have had to do that weeks ago.”

Maas said the German government would follow closely the vote of confidence in May, but that her fall would only make the situation more complicated.

“For the negotiations we need a stable government,” he said.

On a possible delay to Brexit, he added: “It will only make sense if there’s a way which has as its goal to reach a deal between the EU and Britain and at the moment there’s not a majority viewpoint in the British parliament”.

The former Ukip leader, Nigel Farage, in Strasbourg, said the UK had suffered from a “total failure of leadership”, and accused the prime minister of giving in to the EU’s negotiators.

“If you appease bullies they always come back for more. She has behaved like a leader defeated in war,” he said.

• This article was amended on 17 January 2019 to correct Peter Altmaier’s position from finance minister to economics minister.