Hundreds of business owners have threatened to leave Britain if Rachel Reeves presses ahead with an expected tax raid in her Budget later this month.

Nearly half of 500 surveyed business owners said they would consider moving their companies overseas if the Chancellor makes big tax rises, according to wealth managers Evelyn Partners.

Toby Tallon, tax partner at Evelyn Partners, said the company is grappling with an influx of queries from worried business owners since Sir Keir Starmer warned in August that the Budget was “going to be painful”.

Mr Tallon said: “They are anxious about what any potential tax changes could mean for them personally and their businesses, with some mulling the option of becoming non-resident.”

Ms Reeves is poised to launch the biggest Budget tax raid in history on Oct 30, with expected tax rises worth a cumulative £35bn. The Chancellor is scrambling to fill a £22bn “black hole” in the public finance, while avoiding real-terms departmental funding cuts.

She is expected to announce a fresh raid on capital gains tax (CGT) and a rise in employer National Insurance rates.

There are also fears that Ms Reeves will curtail business relief on inheritance tax, which benefits families inheriting a business or its assets, including shares in unlisted companies.

Higher CGT rates would not only push the wealthy to relocate but would put the brakes on entrepreneurs starting new companies, Evelyn Partners’ survey found.

A total 46pc of surveyed business owners said higher CGT rates would put them off starting a new business in the UK.

Ms Reeves’ Budget tax rises will come on top of Labour’s manifesto promises to introduce VAT on private school fees and tighten tax loopholes for wealthy “non-doms”.

Labour has ruled out increasing the headline rate of corporation tax, as well as committing to not raise income tax, employee National Insurance, or VAT.

Mr Tallon said the rapid shift to homeworking since the pandemic proves companies are able to move their operations around quickly.

He said: “With the technology available today some business owners may decide to up sticks and move either themselves or their operations – or both – abroad if they felt they weren’t being made welcome in the UK.”

The survey was conducted by Censuswide on behalf of Evelyn Partners that spoke to the owners of companies with a turnover of £5m or more.