There are reportedly fears on the EU side that a post-Brexit British economy, freed from the burden of EU regulation, will be able to suck jobs and investment out of Europe.

As a result, to build unity, EU nations are believed to be planning that Britain signs up to a “level playing field mechanism”.

Under the mechanism, Britain would be tied to EU standards in return for access to the single market and hit by penalties, such as tariffs, if a future British government, for example, subsidised its car industry or sought competitive advantage through new banking regulations.

EU negotiators are also said to be plotting to block talks on financial services, thus maintaining the City’s access to the single market, as well as aviation rights for British owned airlines.

One senior EU Commission official said: “Why would we give these away? In return for what? The question of financial services and aviation will be settled at the end of the negotiations and the price will be high.”

News of the EU’s reported plans have come as it was last night revealed that nearly half of Britain’s business leaders are “optimistic” about their firm’s prospects next year in spite of wider concerns about Brexit and the economy.

Research carried out for the Institute of Directors found 47% of bosses were "quite optimistic" or "very optimistic" about the outlook for 2018 for their companies.

In contrast, only 17% were either quite or very pessimistic about the coming 12 months. Just over a third (36%) were neither positive nor optimistic about next year.

Yet nearly half (47%) of the 762 business leaders in the survey were pessimistic about the wider outlook for Britain's economy.

The findings are likely to give further weight to the argument that British firms are defying gloomy claims about the country's economic prospects as the departure from the EU approaches.

The research follows a report from the Centre for Economics and Business Research that found the effects on the UK economy following the referendum vote to leave the EU had been less than expected.

Britain was also on course to overtake France in the world economic performance rankings next year, the report said.

Meanwhile, another report yesterday forecast growing demand for computer security staff, data analysts, accountants and civil engineers in 2018.

Research by recruitment firm Hays showed that just over half the UK workforce would be looking for a new job next year, while three out of four employers planned to recruit staff.

Hays said its survey of 17,500 employers and workers found that competition for jobs would be high in 2018, but the outlook for those looking to move was "positive".