Theresa May will harm all other sectors of the economy if she cherry-picks a post-Brexit trade deal for the City of London, new research shows.

The Prime Minister is believed to be ready to pay billions of pounds into the EU budget after Britain leaves the EU to maintain close single market access for financial services.

But the research, by an independent think tank, says all sectors of the economy – including manufacturing, retail, professional services, energy, digital and creative – are just as dependent on the single market.

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Therefore, a “sector-by-sector” approach will fail to prevent the damage from a hard Brexit, which will “reverberate throughout the economy”.

The study will be published as key figures from Britain’s political parties join forces to put pressure on the Government to “put membership of the single market at the heart of their negotiating strategy”.

Conservative MP Anna Soubry shared a stage on Monday with former Liberal Democrat leader Nick Clegg and Labour MP Chuka Umunna, at an event for the Open Britain campaign.

Ms Soubrey insisted there are no “inevitable outcomes” from the referendum result, saying: “There is no mandate for one particular Brexit option. The only question on the ballot paper was whether to leave, which we will, but how we execute our extraction must be debated.”

Pro-Brexit MPs who argue Britain can end free movement, financial contributions to the EU and the jurisdiction of the European Court of Justice are guilty of a “simplistic fantasy”, Ms Soubrey said.

Mr Clegg said that leaving the single market – far from cutting regulation – would “lead to reduced trade due to an increase in regulatory trade barriers”.

“The challenge we are making to those who think differently is this – which sectors of our economy should be the lowest priority when it comes to negotiating an FTA [free trade agreement]?” he warned.

And Mr Umunna added: “Every major sector of our economy is linked to the single market and could be harmed through an arrangement that prioritises one sector over another.

“It is dishonest to deny any cost exists. In short, cherry-picking winners creates losers – and I am not aware of anyone proposing or voting for creating economic losers.”

The research, carried out for Open Britain by the Centre for Economics and Business Research, rejects cherry-picking because “there is considerable linkage between the sectors”.

Crucially, it warns: “Whether the UK is inside or outside of the single market, EU regulations cannot be avoided if Britain wishes to trade with the European Union.”

An FTA would leave Britain as “a rule-taker for industries where it wishes to secure access” – without the same influence over decision-making that it enjoys as a single market member.

Ms May appears determined to pull Britain out of the single market – as the price for imposing curbs on free movement of people – while striking individual deals for the City and the car industry, for example.