Steph Court, of accountancy firm RSM, said: “When it comes to capital gains tax, employee shareholders are largely on board. »

In 2022-23, around 350,000 workers obtained options through SAYE, according to official figures.

Employees can save up to £500 per month in this scheme and, at the end of the three or five year contract, they can buy their company’s shares at an already agreed price. If the current share price is higher than the purchase price, then the employee can sell at a profit – otherwise he gets his savings back as well as any interest or bonuses tax-free.

Experts are concerned that many workers participating in SAYE are not taking the necessary steps to protect their investment profits from capital gains tax. Shares under SAYE must be transferred into a tax-free package such as an individual savings account (Isa) to avoid capital gains tax.

For comparison, shares held under another stock option program called the Share Incentive Plan (SIP) will be exempt from capital gains tax as long as they remain in the plan until ‘at the point of sale.

The previous government held a consultation on share plans for all employees, but did not respond to its call for evidence before the election.

During this consultation, ProShare urged the government of the day to introduce a £10,000 capital gains tax allowance for tax-efficient share schemes.

ProShare said the erosion of the tax benefits of SAYE schemes could see them “disappear” altogether.

Mr Tompsett said: “The Government’s own research shows that when participation is widespread among employees, productivity and financial resilience increase.

“But many are now discouraged by the increased complexity, and it is the lowest income earners who are most likely to stop engaging.”

He added: “Our research shows that a significant number of participating employees do not have any other form of savings. These are ordinary workers who the government has promised not to tax, and we urge the Chancellor to respond to the consultation or risk employee share schemes disappearing under her watch.”

HM Treasury has been contacted for comment.