The EU’s trade commissioner has suggested there could be a last-minute trade-off with Brussels offering the City of London access to European markets in return for European fleets retaining their fishing rights in British waters.

The UK’s financial services sector will lose its automatic right to serve Europe-based clients at the end of the transition period and the EU will need to negotiate access to UK waters for its fishing boats.

Phil Hogan, the former Irish minister who is now trade commissioner in Brussels overseeing the next stage of the Brexit negotiations, told the Irish Independent: “There certainly will be trade-offs, particularly at the end of the negotiations. The EU will be seeking concessions on fishery access and the UK will very probably be seeking concessions on financial services.”

Hogan, a longstanding critic of prominent Brexiters including Boris Johnson, described claims that the EU would be put under pressure to seal a deal by parallel UK-US negotiations as “fairytale economics”.

Negotiations on the future relationship between the EU and the UK after 31 January, the scheduled date for Brexit, are expected to start in early March once both sides have settled positions on the main issues.

EU diplomats were presented with the main principles of the free trade agreement on Monday in which “access to waters and quota share for fisheries” would be made “within the context of the economic partnership”.

Speaking in Luxembourg on Monday, Ursula von der Leyen, the European commission president, reiterated that the British government would also need to sign up to a series of commitments on state aid, environmental and labour standards to allow tariff- and quota-free trade.

She said: “Great Britain is our friend, the Brits are our friends, it is a friendship that has been growing for a long time but we have to break new ground with each other, and here it applies as well: it is the decision of Great Britain how close or distant of the biggest single market in the world they want to be.

“The closer they are, meaning a level playing field, the more they are ready to respect the European rules, the easier accession to the European single market will be. The further away, the less there is of a level playing field, the more difficult their access to the European single market will be. It is a decision Great Britain has to make and in the negotiations we will have to sound out the scope that we want to use to then determine the negotiations accordingly.”

Last week, Andrej Plenković, Croatia’s prime minister, whose country is taking over the presidency of the EU, conceded that Brussels would be unashamedly “political” and could threaten to block the City of London’s access to European markets if Johnson tries to exempt the UK from its laws. He also warned of the risk of skirmishes at sea similar to those during the 1970s cod wars if a deal on fishing rights was not secured.

Asked whether the EU would use its power to switch off the City’s ability to serve European clients, to gain leverage in the coming negotiations with Britain, Plenković said: “I wouldn’t go into the vocabulary of weapons but what I have learned in international and European negotiations [is] that all arguments and considerations are treated as political.”