The EU's top Brexit negotiator Michel Barnier yesterday warned Britain there were no grounds for walking away without a deal, a scenario that would only harm the UK's interests.

"No deal would make a lose-lose situation even worse ... in my mind, there is no reasonable justification for a no-deal," Barnier said, referring to recent suggestions by British ministers that London could go its own way if the talks fail.

"A fair deal is far better than no deal," he told an ELI panel on Brexit, repeating the phrase twice in English.

Britain and the Eli began the formal Brexit talks last month based on Barnier's timetable of dealing first with the rights of more than three million ELI citizens in Britain, and more than one million Britons living in Europe.

Then follows the thorny issues of Britain's estimated 100-billion-euro ($112 billion) exit bill and future of the border between Northern Ireland and the Republic of Ireland, which remains in the ELL

Only once "sufficient" progress has been made on these issues, will the European Union consider London's demand for talks on its future relationship with Brussels, including all important trade arrangements.

Barnier told the panel the ELI would make no compromises on this agenda, insisting repeatedly that Britain could not expect to cherry-pick its ties with the bloc as many British politicians say it should.

Prime Minister Theresa May's spokesman said that it "wasn't new that some on the EU side have strong feelings" about Brexit, but that both parties would benefit from a trade deal.

"We're just at the beginning of the negotiations, but I would say that the most frictionless possible trade between the UK and the EU is clearly in the interests of both sides," he said.

"We want a comprehensive free trade agreement and a new customs agreement."