Britain will have to stay aligned to EU rules in a whole set of areas after Brexit if it wants a trade deal, the bloc's chief negotiator has said.

Michel Barnier said tariff- and quota-free access to EU markets was dependent on the inclusion of "a mechanism to uphold the high standards we have on social, environmental, tax, and state aid matters today and in their future developments".

He also said a deal was "conditional" on an agreement giving EU fishing fleets access to British waters, and that it would be governed by the EU's European Court of Justice.

How aligned the UK stays to EU rules is set to be a major battleground in the coming trade talks. Mr Barnier warned that the EU would be "very demanding" in its stipulations on the UK and that its objective was "to ensure that [regulatory] divergence doesn't become an instrument for unfair competition whereby there would be disadvantages for EU industry".

The negotiator's suggestion that "future developments" in EU rules should be incorporated into UK law is likely to be a particular stumbling block, as it rules out a simple "non-regression" clause in the deal keeping British standards at the level they are now.

The European Commission on Monday published its negotiating mandate, which the chief negotiator was unveiling at a press conference in Brussels. It will have to be approved by member states at a meeting later this month.

It comes the same day as Boris Johnson lays out the UK approach to talks in a speech in London. The prime minister says he would be willing to accept tariffs in trade with the EU if it means the UK can diverge on its regulations.

But if the prime minister fails to negotiate a zero-tariff and zero-quota trade agreement, there will be tariffs and quotas payable on goods moving between different parts of the United Kingdom – across the Irish Sea. This is because Mr Johnson's withdrawal agreement puts a customs border between Great Britain and Northern Ireland. There will be customs and regulatory checks whether or not a deal is negotiated.

In a separate complicating issue, the EU's negotiating mandate says the trade deal will not apply to Gibraltar. The mandate says that any "separate agreements" will require "a prior agreement of the Kingdom of Spain" – effectively giving the Spanish government a veto.

Mr Barnier would not be drawn on the details of how the regulatory alignment could be enforced, telling journalists in Brussels: "I can't get embroiled in the details of the mechanism, that will all be discussed in the negotiation".

Regarding the European Court of Justice's role in overseeing the deal, one official said: "The European Court of Justice's role is important: it will apply to the whole agreement. Whenever there is a question of interpreting EU law, the only court that can do that is the ECJ. We cannot invent a new court, a new legal system to do this. Of course, international agreements are EU law, so they are part of the interpretation that the court has to give."

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After 47 years in the European fold, the country leaves the EU at 11:00pm (2300 GMT) on Friday, with a handful of the most enthusiastic supporters gathering opposite the Houses of Parliament 12 hours before the final countdown. (Photo by ISABEL INFANTES / AFP) (Photo by ISABEL INFANTES/AFP via Getty Images) ISABEL INFANTES AFP via Getty Brexit celebrations in Parliament Square People wave British Union Jack flags as they celebrate Reuters Brexit celebrations in Parliament Square Pro-Brexit demonstrators celebrate on Parliament Square on Brexit day Reuters Brexit celebrations in Parliament Square A pro-Brexit supporter jumps on an EU flag PA Brexit celebrations in Parliament Square LONDON, ENGLAND - JANUARY 31: Pro Brexit supporters gather ahead of the Brexit Day Celebration Party hosted by Leave Means Leave at Parliament Square on January 31, 2020 in London, England. 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(Photo by ISABEL INFANTES / AFP) (Photo by ISABEL INFANTES/AFP via Getty Images) ISABEL INFANTES AFP via Getty Brexit celebrations in Parliament Square Brexit supporters gather in Parliament Square, London, as the UK prepares to leave the European Union after 47 years. PA Photo. Picture date: Friday January 31, 2020. See PA story POLITICS Brexit. Photo credit should read: Jonathan Brady/PA Wire Jonathan Brady PA Brexit celebrations in Parliament Square LONDON, ENGLAND - JANUARY 31: Pro Brexit supporters gather ahead of the Brexit Day Celebration Party hosted by Leave Means Leave at Parliament Square on January 31, 2020 in London, England. At 11.00pm on Friday 31st January the UK and Northern Ireland exits the European Union, 188 weeks after the referendum on June 23rd, 2016. (Photo by Jeff J Mitchell/Getty Images) Leon Neal Getty Brexit celebrations in Parliament Square People draped in UK flags walks across Parliament Square during a rainfall in London, Friday, Jan. 31, 2020. 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They added: "It's not a choice, its reality – if it's a question of EU law it's for the ECJ to do that."

Under the EU's governance proposal, a joint disputes committee would decide whether any issue was a matter of EU law or not – and call in the ECJ if it was. If the issue is deemed not to be a matter of European law it would be decided by the committee itself.