The EU will tell the UK that it must maintain higher labour and environmental standards than some of its own member states and that it will put the socioeconomic interests of its fishing communities at the centre of its post-Brexit negotiating strategy, diplomats have heard.

Diplomats briefed by the European commission on Tuesday were informed that the UK would need to commit to staying beyond the common basic minimum of standards applied to EU member states.

The EU will insist that the British government signs up to the “non-lowering of higher domestic labour and environmental standards in order to encourage trade and investment”.

The UK has “gold-plated” EU regulations in key fields including the environment and it will be bound to maintain those under the deal being plotted out in Brussels.

The EU also expects the UK to sign up to Brussels’ state aid rules with an “independent enforcement authority in the UK” working in “close cooperation with [the European] commission”.

According to slides published by the European commission on Tuesday, the intention is to build what some sources have described as a “punishment clause” into a future deal.

The EU would be granted the possibility of “autonomous remedies – interim measures to react quickly to disruptions of the equal conditions of competition in relevant areas” should the UK lower its standards.

According to the slides, the commission foresees the commitments of the UK on state aid and environmental and labour standards to also evolve through a joint committee that will set “higher standards or include additional areas”.

On the issue of fishing rights in British waters after Brexit, diplomats were told that beyond “sustainability and conservation” an objective of the EU would be protecting the often comparatively poor fishing towns and villages on the North Sea coast.

The UK has insisted that post-Brexit fishing policy in British waters would be determined by scientific advice and innovation in practices. The government has also stated in official communications that “market access for fisheries products is separate to the question of fishing opportunities and access to waters”.

But in the slide presentation, commission officials insisted that socioeconomic factors would play a role in the unprecedented negotiation and restated the intention of the EU to link the level of access given to UK goods in Europe.

The officials told the diplomats that the fisheries negotiation would be done “within the context of the overall economic partnership, including a direct link with negotiations on trade in goods”.

Under the Common Fisheries Policy the EU’s seas and 100 fish stocks are in effect common to the 28 EU member states.

The total number of each species of fish that can be taken from various zones in the EU’s seas each year is settled by the member states on the advice of scientists, to ensure sustainability.

Each country has a species-by-species quota they can take from that European haul under quotas that have been fixed since 1983 on the basis of the recorded catches of the various national fleets between 1973 and 1978.

According to recent estimates, 33% of the catches of the European fishing fleet are caught in what will soon be claimed as British waters.

Facebook Twitter Pinterest Ursula von der Leyen has stressed the difficulty of reaching agreement on trade issues by the end of this year. Photograph: Frederick Florin/AFP via Getty Images

Both sides have committed to negotiating a new framework for deciding fishing rights by 1 July although EU sources believe that the sheer complexity of the issue will result in the talks going deep into the year.

Speaking in Strasbourg, the European commission president, Ursula von der Leyen, stressed the difficulty of reaching agreement on the many issues in trade and beyond by the end of 2020 and used Boris Johnson’s previous claim to want “cake and to eat it” against him.

She said: “We have to make enormous progress – this is decisive – until the summer and here we have to decide on, or it’s the UK’s choice to decide on, how close or how distant they want to be from the EU.

“But that also means from the single market in other terms. You cannot have no free movement for people and then expect to have free movement for goods, capitals and services.

“You cannot expect to have a level playing field if there’s a huge divergence in taxation or social standards or environmental standards.

“So it’s the choice of the UK how far they want to align or diverge. But this is decisive for how good the access to the single market will be or not, in short. It’s the old proverb, ‘You cannot have the cake and eat it at the same time’.”