Foreign Secretary Boris Johnson, the chief cheerleader of the Vote Leave campaign, has told the EU to "go whistle" over plans to stick the UK with a €100bn (£88bn) divorce bill.
The former Mayor of London, speaking in the House of Commons on Tuesday 11 July, also said that the government had no plans for a 'no deal' scenario with Brussels because the UK intends to secure a "great deal".
"I'm sure that my honourable friend's words will have broken like a thunderclap over Brussels and they will pay attention to what he has said," Johnson said in response to fellow Brexit-backing Tory MP Philip Hollobone.
"He makes a very valid point and I think that the sums that I have seen that they propose to demand from this country seem to me to be extortionate and I think to 'go whistle' is an entirely appropriate expression."
Labour's Shadow Foreign Secretary Emily Thornberry later asked Johnson to spell out what leaving the economic and political bloc without an agreement would mean. "Can he reassure us that if he's not prepared to tell us publicly at the very least he has a detailed private plan to manage that risk?" she said.
Johnson responded: "There is no plan for 'no deal' because we are going to get a great deal."
The foreign secretary showed a "shocking level of complacency", according to Liberal Democrat Brexit spokesperson Tom Brake MP. "These kind of glib assurances are straight out of the [Donald] Trump playbook," he said.
"It is simply not good enough when people's jobs, living standards and rights are all on the line. People should be able to judge Boris Johnson on his actions not his words, with the chance to reject a disastrous Brexit deal and stay in the EU."
The two-year-long talks between the EU and UK kicked off in June, with Brexit Secretary David Davis agreeing to a timetable proposed by Michel Barnier, the EU's chief negotiator. The move means discussions around the future rights of the more than 3 million EU nationals in the UK and the 1.2 million Britons on the continent will be prioritised.
Elsewhere, the parties are expected to debate a potential divorce bill for the UK, with the Financial Times reporting that the total could reach up to £100bn.