European Union leaders have warned they will not tolerate any effort by the British government to override the agreed Brexit treaty and will insist on tough enforcement measures for any trade deal with the United Kingdom.

Michel Barnier, the EU's chief negotiator, will be urged by the bloc's leaders to ensure that so-called level playing field guarantees for EU businesses competing with British firms have the right to take action if the UK breaches its commitments, the Financial Times reported.

The EU wants to secure consistent rights to fish in British waters, while Britain wants a deal in which quotas are set each year

At an EU summit starting on Thursday, France and other fishing nations will highlight the importance of preserving quota rights in British waters, the newspaper reported.

READ MORE: FT: EU leaders to insist on tough Brexit deal enforcement powers

The bloc wants to secure consistent rights to fish in British waters, while Britain wants a deal in which quotas are set each year.

British Prime Minister Boris Johnson set a deadline of this Thursday for agreement on a trade deal, to coincide with the summit in Brussels.

Barnier is reported as seeking a few more concessions from the UK before entering the last intense phase of negotiations on a deal, and has said that Oct 31 is a more "realistic deadline".

Britain departed from the EU on Jan 31 but remains in a transition period until the end of this year. Rules, regulations and budget payments continue until then.

Both sides have said an agreement on any trade deal needs to be struck in October to ensure sufficient time for ratification.

'Significant gaps'

The British prime minister's office confirmed that Johnson spoke on the phone with German Chancellor Angela Merkel on Sunday, and told his counterpart that progress must be made in the EU trade talks to bridge the "significant gaps".

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The prime minister held similar discussions with French President Emmanuel Macron on Saturday.

Downing Street said Johnson told Merkel that "while achieving a deal in the coming days would be beneficial for both sides, the UK was also prepared to end the transition period on Australia-style terms". The EU trades with Australia on the basis of World Trade Organization rules, according to the Week website.

Barnier last week urged EU governments to give him more room to move on fishing rights, according to the Financial Times.

The UK's chief negotiator, David Frost, said Britain was willing to discuss state-aid policy commitments that "go further than you normally do in a free-trade agreement".

The Financial Times reported that European leaders would press Barnier to ensure any level playing field arrangements could be enforced, and that the bloc could take "interim" and "autonomous" measures, as well as "cross-retaliate" against different sectors of the UK economy.

jonathan@mail.chinadailyuk.com