Facing questions in the House of Commons, the foreign secretary told MPs that the government had “no plan for no deal” because of its confidence over securing a strong Brexit settlement with the bloc.
A Downing Street spokesman later clarified that contingency planning was taking place for all Brexit scenarios.
Taking questions from MPs, Mr Johnson was asked about the likelihood of a large Brexit bill by Eurosceptic Tory Philip Hollobone, who said: “Will you make it clear to the EU that if they want a penny piece more then they can go whistle?”
The Foreign Secretary replied: “I’m sure that your words will have broken like a thunderclap over Brussels and they will pay attention to what you have said.
“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.”
Meanwhile, David Davis revealed that a Scottish Parliament vote to approve a key piece of Brexit legislation would take place early next year.
The Brexit Secretary told a House of Lords Committee that a legislative consent motion on the Repeal Bill would be held at Holyrood at the start of 2018, but would not be drawn on the consequences if MSPs vote the motion down.
Asked about Mr Johnson’s comments, the Brexit Secretary laughed before telling peers: “Bluntly, I wouldn’t worry. I mean you will have to get the Foreign Secretary here to explain his views if you really wanted to. I’m not going to comment on other ministers.” Earlier, Mr Davis told a meeting of the cabinet that the Repeal Bill, which will incorporate Brussels regulations into UK law, will be introduced and have its first reading in the House of Commons on Thursday.
The Foreign Secretary’s comments come after Number 10 sources played down suggestions that Theresa May plans to walk out of Brexit talks in September to show defiance over EU demands for a divorce bill worth tens of billions of pounds.
European Commission president Jean-Claude Juncker has suggested that the bill, which covers outstanding liabilities for programmes which the UK signed up to as an EU member, as well as ongoing costs including staff pensions, could be around £50 billion, while unconfirmed reports have claimed it could reach almost twice that figure.
Mr Johnson also appeared to mock Jeremy Corbyn over the Labour party’s support for leaving the European single market.
He said it was “striking” to see “how much unanimity there really is between the two sides of the chamber” on the fundamental points of Brexit, and said “the leader of the Labour party seems to be very much on all fours with the objectives” of the government.