The EU's chief Brexit negotiator, Michael Barnier, has warned the UK government the "clock is ticking" on the parties' two-year-long divorce talks, as he hit back at Boris Johnson in Brussels on Wednesday 12 July.
The French politician issued the salvo just a day after the British Foreign Secretary told MPs the EU should "go whistle" over an "extortionate" Brexit bill.
"I am not hearing any whistling, just a clock ticking," Barnier said. EU chiefs are apparently planning to demand that the UK pays €100bn (£89bn) for splitting from the bloc.
Banier, who denied that the EU was seeking to punish Britain, said: "It is essential that the UK recognise the existence of financial obligations, which are simply the result of the period during which they were members of the EU."
He added: "What I have to say is that the quicker we move forward, and that's the spirit in which I'm working on these phase one subjects, the sooner we will be able to discuss our future relationship."
Banier also revealed that he plans to meet with Labour leader Jeremy Corbyn, First Minister of Scotland Nicola Sturgeon, First Minister of Wales Carwyn Jones and a delegation from the House of Lords' EU Select Committee. "Of course, I will only negotiate with the UK government," he said.
David Davis, Barnier's British counterpart as Secretary of State for Exiting the EU, faced a grilling from the group of cross-party peers on Tuesday.
The senior Conservative praised Barnier as a "very French, very principled" man, but warned that his negotiating guidelines – set by the EU Council and EU Commission – were "narrow".
Elsewhere, he described the residency rights of the more than three million EU nationals in the UK and the more than one million Britons on the continent as an "issue of civilisation as much as anything else", with Davis and Barnier prioritising the subject in the negotiations.
Prime Minister Theresa May, despite losing her majority in the House of Commons at the general election in June, still plans to split from the EU's single-market and customs union.
The Tory premier used a post-election speech to call for contributions from opposition parties to her government's Brexit plans. Corbyn, who has called for a "jobs-first Brexit" reacted by sending May a copy of Labour's general election manifesto.