The United Kingdom's position on Brexit is based on "pure illusion," European Council President Donald Tusk told reporters in Brussels after a meeting of EU leaders.
His comments Friday came a day after UK Prime Minister Theresa May and senior Cabinet ministers spent hours at her official country retreat hammering out London's position in future Brexit negotiations in the face of deep divisions within her Conservative Party.
May is expected to set out her vision for Britain's future trading relationship with the European Union in a speech next Friday. But Tusk's remarks raise questions over how well it will go down in Brussels.
"I'm afraid that the UK position today is based on pure illusion. It looks like the 'cake philosophy' is still alive," Tusk said. "From the very start, there has been a key principle of the EU 27 members that there can be no cherry-picking and no single market - la carte."
Tusk has previously accused May of holding a philosophy of "having her cake and eating it" over Brexit by trying to keep the benefits of EU membership without having to follow its rules.
Tusk said he had informed EU leaders that he would present draft guidelines in the future EU-UK relationship at a European Council summit next month.
"Our intention is to adopt these guidelines, whether the UK is ready with its vision of our future relations, or not. Naturally, it would be much better if it were, but we cannot stand by and wait. I hope to have some more clarity about the UK plans next week, when I meet Prime Minister May in London."
Tusk's meeting with May is scheduled to take place Thursday, a day before she gives her speech on trade.
Opposition Labour leader Jeremy Corbyn will give a speech Monday in which he could pave the way for a government defeat over Brexit, Britain's Guardian newspaper reported, by backing a move by rebel Conservatives to keep Britain in a customs union with the European Union.
May gathered key members of her fractious Cabinet this week for an "away day" at her country retreat, Chequers, in a bid to galvanize support within her divided party for a common position on Brexit.
She needs to establish Britain's terms for the transition period that will follow its departure from the EU in March 2019. However, that process has been fraught with difficulty in the past few months.
UK media reports indicate that Cabinet ministers agreed Thursday on an approach of "managed divergence" by which Britain would take control of its own regulations but maintain the standards required by the EU in certain key areas to protect trade and jobs.
"The Brexit committee made a step forward yesterday by agreeing (to) the basics of the future relationship," a Downing Street representative told CNN.
Chancellor of the Exchequer Philip Hammond tweeted Friday that the Chequers meeting had been "positive and constructive" and that "steady progress" was being made toward delivering Brexit.
Speaking Tuesday in Vienna, Austria, David Davis, secretary of state for exiting the EU, described what Britain aspired to as "a race to the top in global standards," which meant that British regulators and institutions could continue to be recognized by the EU.
"We start from a position of total alignment, with unprecedented experience in working with one another's regulators and institutions," Davis said.
"The agreement we strike will not be about how to build convergence, but what we do when one of us chooses to make changes to our rules. Neither side should put up unnecessary barriers during this process."