The Brussels negotiator insisted both sides must make “tangible” progress on all areas of the trade deal in the hope of preventing the Prime Minister from using access to Britain’s fishing waters as a bargaining chip in the future. After opening talks with his UK counterpart David Frost, Mr Barnier said: “We must advance across all areas: it is our objective to make tangible progress by June.” 

The Frenchman has previously warned maintaining access for European fishermen to Britain’s waters would come as the price for any trade deal.

European capitals believe the UK Government has held back its fisheries plan in the hope of securing more favourable terms, in areas such as financial services, further down the line.

Mr Frost, the Prime Minister’s top Europe adviser, has yet to publish a draft fisheries text as part of a series of proposals sent to the European Commission.

Britain has published a document that states its negotiating team is seeking to scrap the existing Common Fisheries Policy model in favour of annual negotiations using science to establish quota shares.

Both sides are now focused on making progress – with week-long talks also scheduled for May and June – ahead of a high-level meeting between Mr Johnson and Ursula von der Leyen, the European Commission’s president.

Mr Frost said: “We look to make good progress towards an agreement based on friendly cooperation between sovereign equals, as we set out on February 27.”

Talks got underway amid a gloomy atmosphere after previous rounds of trade negotiations were abandoned because of the coronavirus pandemic.

Brussels has denied significantly altering its priorities after Mr Johnson ruled out extending the Brexit transition period beyond the end of the year.

An EU Commission spokesman said: “The issue now is to try to make sure that the UK’s exit from the EU and the transition period, if it’s not extended further from the end of the year, set a threshold for our negotiations with the UK going forward, pandemic or no pandemic.

“Of course we have come up with a very comprehensive agenda on all kinds of different topics and let me reiterate that we have a busy week ahead of us and we’re going to work as hard as we can to ensure progress.”

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Fisheries, as well as the “level-playing field” on fair competition, are expected to feature prominently during this week’s negotiations.

They remain just two of the outstanding issues that EU sources say there is a “very, very big gap” between both sides’ positions.

Officials will negotiate in 11 separate work streams in a bid to speed up the process.

Talks will conclude on Friday before being reconvened on May 11, and then again on June 1.