Barnier said there was no fixed sum for the UK's financial obligations, and that the figure would be calculated using a "methodology".
He also said that, while the UK has to respect its obligations towards the EU, the same is true the other way around.
"There is no punishment, there is no Brexit bill, the financial settlement is only about settling the accounts," he told a news conference.
In the wake of reports of a disastrous dinner between UK Prime Minister Theresa May, European Commission chief Jean-Claude Juncker and Barnier last week, Barnier said no one should believe Brexit would be easy.
"Some have created the illusion that Brexit will have no material impact on our lives or that negotiations can be concluded quickly," he said.
At the same time, he acknowledged that he thought his counterparts in London were "aware of the urgency of the matter and of their responsibilities".
There was never any prospect that the histrionic UK general election debate – “all about Brexit”– would contribute any clarity to the Brexit negotiating process. The best Prime Minister Theresa May could hope for was to find in it some means of painting herself as resolute and unbending, another Margaret Thatcher who would not be shaken by the dastardly Europeans. Above all, no floundering Jeremy Corbyn.
And she got that in spades with the leak of the details of her lunch last week with Commission President Jean-Claude Juncker. No matter that it revealed apparently absurd misapprehensions, whether genuine or not, about EU procedures and law ... Juncker called her ideas “in a different galaxy” – how many voters will even know? The prime minister cloaked herself in the mantle of Britannia as she dismissed “Brussels gossip”.
How did things get so heated so quickly? In a word – money. At the risk of oversimplifying, at least some in the EU seem to put the final bill at over 100 billion euros ($109 billion), while at least some in the U.K. government argue that there's nothing to pay, period. That leaves a lot of room for arguing.
The EU's top Brexit negotiator, Michel Barnier, outlined Wednesday that he wants to agree to a "global settlement" on outstanding obligations before starting to talk about how the two sides will regulate trade, investment, and citizens' rights after March 2019, when Britain formally withdraws from the union. May, by contrast, wants to talks about a future trade agreement to run in parallel with the talks on the divorce settlement, not least because business wants to know as soon as possible the terms on which it will be able to buy from and sell to Europe after 2019. Foreign investors, such as Wall Street banks like JPMorgan Chase, want to know whether it's even worth staying in the U.K. after Brexit and are already preparing to move people from London to financial centers in other EU countries.
While both Ms May and Ms Merkel benefit domestically from taking a tough stance, the EU negotiators, too, love the escalation because they know that Ms May can only be bluffing. here is, for example, no reason for her to know about the European Medicines Agency's 500 million euro (18.8 billion baht) unbreakable, 25-year lease in Canary Wharf.Since the EU didn't initiate Brexit, it doesn't want to pay to break it off and move the EMA elsewhere -- even if the lease wasn't a smart idea in the first place. Since the EU didn't initiate Brexit, it doesn't want to pay to break it off and move the EMA elsewhere -- even if the lease wasn't a smart idea in the first place.
Mr Juncker and his team, free of responsibility for running any single country, deal with these cross-border housekeeping matters on a daily basis. They also know how detailed trade talks can get: They've hammered out quite a number of them, something the UK hasn't had to do since it's been a EU member.
Ms May, of course, could find the expertise among UK officials with EU experience -- but, well before Brexit, the British presence in EU institutions was gradually waning. As far back as 2013, the UK parliament's Foreign Affairs Committee was complaining that not enough Brits were taking EU employment tests to compensate for retiring staffers. The UK has long treated the EU as a nuisance and worked harder on opt-outs than on trying to learn its ropes. Now, it doesn't quite understand what the EU wants and why it wants it.