Small business leaders have accused Boris Johnson of failing to protect them from the damage Brexit will inflict – with one third ready to quit the UK to escape it.

The prime minister’s strategy is savaged in a pre-Brexit survey revealing widespread gloom about the prospects for smaller firms outside the EU, which has been shared with The Independent.

It shows close to half of owners fear a “negative” impact on their businesses – while almost a third fear losing full access to the EU market with the loss of frictionless trade, and a further quarter in the dark.

Only 22 per cent said they had no regrets about the divorce, with more giving the loss of “free trade” with the EU (35 per cent) and of ease of travel (29 per cent) as their biggest regret.

No less than 60 per cent of respondents said they were dissatisfied with the government’s approach to protecting British businesses from the Brexit fallout.

Most strikingly, one third said they would consider moving either their businesses or themselves across the Channel to remain part of the EU and its huge market.

“If I were Boris Johnson I would be pretty worried – I don’t think the government is really looking at small companies,” said Ott Vatter, managing director of the organisation that carried out the poll.

The survey comes amid rising concern that the government – in its desire for “no alignment” with EU regulations – is prepared to sacrifice business interests.

Some trade barriers and border checks are inevitable with departure from the single market and customs union, even if Mr Johnson achieves the no tariffs, no quotas deal he seeks.

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Firms have also spoken out about the threat to the right to transmit data, while financial services companies will lose “passporting” rights to trade in the EU and other companies will lose EU grants.

The Federation of Small Businesses has urged the prime minister to “waste” no more time explaining what lies ahead – with a major speech expected at the start of next week.

The survey seen by The Independent was carried out among just over 1,000 small business owners, freelancers and entrepreneurs by the research company Censuswide.

Respondents were quizzed in mid-December, mostly after Mr Johnson’s general election triumph, on behalf of e-residency, the Estonian government’s programme enabling firms to create “virtual companies” to trade in the EU from the UK.

Mr Vatter, the managing director, said there was evidence that financial services companies are already moving to France and Germany in preparation for the realities of Brexit at the end of the transition period, in December.

“It is not surprising that there is still a great deal of confusion and apprehension three years after the UK chose to leave the EU,” he added.

“Companies simply have not had the support they need to prepare adequately for Brexit, and this in turn is affecting their sense of security and stability in doing business in the UK.

“The government seems to be focused on big companies – those that make the big revenues – but we are talking here about foot-in-the-door companies that will also face obstacles very soon.”

Mr Johnson has been criticised for failing to expand on the misleading simplicity of his “Get Brexit Done” message, when the momentous task of striking new trade terms still lies ahead.

He only finally acknowledged, on Thursday, that border checks are inevitable and there are fears that next week’s much-hyped speech will fail to answer many questions.

Mike Cherry, the FSB chairman, said on Brexit Day: “As one chapter of Brexit ends, another begins, with little time on the clock to flesh out the crucial details needed to secure an ambitious deal that works for all of the UK.