Britain has accused the European Union of making a sub-standard offer in post-Brexit trade talks, as it urged Brussels to give ground on its proposals to strike a quick deal.

UK chief negotiator David Frost told his EU counterpart, Michel Barnier, that the EU was not offering a "fair free trade relationship between close economic partners".

Instead, the deal on the table was "a relatively low-quality trade agreement coming with unprecedented EU oversight of our laws and institutions", he wrote in a four-page letter.

"It does not have to be like this," he added.

A third round of talks broke up last week, with both sides complaining of deadlock in key areas such as EU access to UK fishing grounds, governance, and the so-called level playing on common standards and competition.

"The EU essentially wants us to obey the rules of their club even though we're no longer members," UK Cabinet Office minister Michael Gove said in parliament earlier.

But he told MPs a free trade agreement was still possible - as long as the EU moved away from its "ideological fastness" and recognised Britain "as a sovereign equal".

Deadline looms

Britain left the EU in January, nearly four years after a landmark referendum in June 2016 that saw voters choose to end nearly 50 years of integration with Europe.

It remains bound by EU rules until 31 December as it tries to secure terms for a new relationship with its biggest trading partner.

A fourth round of negotiations is pencilled in for early June, just weeks ahead of a deadline for an extension to the talks that British Prime Minister Boris Johnson has emphatically ruled out.

Mr Johnson's office released Mr Frost's letter to Mr Barnier after finally publishing a raft of its draft legal texts used in the talks, and a new global tariff regime for January 2020.

"Transparency is very important in negotiations," Mr Barnier responded, pointing out that the EU Commission published its documents more than two months ago.

Mr Frost again outlined Britain's position - that it wants to leave the EU single market and customs union, and is eyeing a free trade agreement (FTA) based on those that Brussels has already struck with countries such as Canada.

He questioned EU demands for "additional, unbalanced and unprecedented provisions... as a precondition for agreement between us".

"We find it hard to see what makes the UK, uniquely among your trading partners, so unworthy of being offered the kind of well-precedented arrangements commonplace in modern FTAs," he added.

Level-playing field proposals, particularly European Court of Justice oversight on state aid rules, would be unacceptable to any democratic country, he said.

"It would mean that the British people could not decide our own rules to support our own industries in our own parliament," he added.

"Similar issues manifest themselves across labour, environment, climate change and taxation," he added, ruling out "any alignment" with EU rules and law.

'Think again'

Securing agreement was always going to be tight, even before the coronavirus outbreak, which struck Mr Johnson, Mr Frost and Mr Barnier themselves and forced the talks online.

But Mr Frost said he was still confident of quickly signing a "modern and straightforward FTA".

"I do hope that in the weeks to come the EU will think again about its proposals in a way that will enable us to then find a rapid and constructive alternative way forward," he added.

Mr Barnier indicated the EU had no plans to back down.

"In the next round (of talks), we must make tangible progress across all areas, including level-playing field and governance," he wrote on Twitter.

Britain's new global tariff schedule, to replace the EU's external tariff on goods from January 2021, would axe duties on about €69 billion of imports, according to ministers.

It will apply to countries with whom the UK does not have a trade agreement.