The door remains open to the European Union if the UK wants to change its mind on Brexit, the most senior leaders of the EU institutions have said.

In a speech to MEPs, Donald Tusk, the head of the European council, suggested reversing Brexit was still a possibility in his mind. “If the UK government sticks to its decision to leave, Brexit will become a reality – with all its negative consequences – in March next year. Unless there is a change of heart among our British friends.”

Tusk recalled the words of the UK Brexit secretary, David Davis, who said in 2013 that “if a democracy cannot change its mind, it ceases to be a democracy”. Quoting these remarks, Tusk said: “We, here on the continent, haven’t had a change of heart. Our hearts are still open to you.”

Jean-Claude Juncker, the president of the European commission, endorsed this conclusion. “[Tusk] said our door still remains open and I hope that will be heard clearly in London.”

Tusk’s emollient tone contrasted with tougher language from some of the key MEPs involved in the process.

Guy Verhofstadt, the European parliament’s Brexit co-ordinator, reiterated warnings that MEPs would not accept any Brexit deal that put the UK in a better position than EU member states. “There cannot be cherry-picking inside the system.”

Manfred Weber, the German politician and leader of the centre-right bloc in the European parliament, attacked the integrity of Theresa May and her government and its choice of priorities.

“The first problem is about honesty, the whole story is a scam,” said the MEP, in a reference to the recent announcement about blue passports.

EU law did not mandate the colour of passports and Croatia has had navy passports for years, Weber said in a withering speech. He expressed scorn that the British government had chosen to say it was changing the colour of passports before announcing its vision for a future relationship with the EU.

“If I was a British citizen I would be deeply worried about the priorities of my government,” he said.

Weber also hit back at “a lot of complaints from our British friends”, referring to Davis’s surprise at criticism of the EU preparations for a no-deal outcome, as well as the chancellor Philip Hammond’s protest that Michel Barnier, the EU’s chief negotiator, has ruled out a special deal for the City. “My message to London,” Weber said, “is please stop complaining, please deliver, give us an outlook about what you want to achieve for the future relationships.”

The British government has called on the EU to be clearer about its goals for the future trading relationship with Britain – a request that has received a near-universal rebuff from EU political and business leaders.

“Tell us what you want,” said the commission’s vice-president, Frans Timmermans. “That would be helpful. We are not leaving the UK, the UK is leaving the EU. We need to know precisely what the UK wants and then we will negotiate. There is no ill-will, no fear.”

The commissioner, a former Dutch foreign secretary, rejected claims by Hammond that Brussels was “paranoid” that a good deal for the UK would push others out of the bloc.

“I don’t really think Philip’s statement rings true to me,” Timmermans said. “At the very beginning, after 23 June, I heard this in a number of member states: ‘We have to watch out that this doesn’t become an attractive thing.’ But it only took a couple of months at looking at what was happening in the UK for public opinion in possibly all the member states to be in more favour of the EU than before.

“Then of course you had the election in the Netherlands, and in France and the change in mood. Even the Five Star Movement in Italy is getting cold feet [on leaving the euro]. The trend is not towards EU leaving, being afraid of a ripple effect. On the contrary. I don’t see that at all.”