The move has led to warnings that Sunak could be looking to claw back the enormous sums spent on bailing the economy out of the Covid-19 crisis.

The request followed a report by the Office for Budget Responsibility (OBR) which said that the growing deficit in government spending was likely to exceed £350bn this year due to the costs of protecting businesses and households during the coronavirus pandemic.

Nathan Long, senior analyst at Hargreaves Lansdown, said: “We’d support a comprehensive review of all capital taxes because we’d like them to be simple and fair. We want a system which incentivises people to invest well and for the long term and encourages wealth to trickle between generations. A formal, holistic review would prevent isolated knee-jerk tweaks which slowly, but surely, erode even the best designed tax systems.

“Capital gains tax currently doesn’t take account of how long people have held an investment, but it should. It also leaves investors semi-trapped in investments to avoid incurring a tax penalty. In the case of those with a second property they want to sell, this doesn’t really promote sale of housing stock to first-time buyers.

“Currently capital gains are taxed at a much lower level than income, so there’s a risk that in this environment, the chancellor will use this as a justification to hike capital gains tax closer to income taxes.”

Tax and advisory firm Blick Rothenberg said the move could be bad news for investors as it was inevitable that any reform would form part of a predicted post-Covid tax raid.

Nimesh Shah, a partner at the firm, said: “After all the good news at last week’s summer statement, this is probably an early indication from the chancellor that CGT is the first tax set to rise. There has been significant recent speculation that the main rate of CGT of 20% is set too low, and some have suggested that it should be aligned to the income tax rates, up to 45%.

“There is a very compelling case for tax reform and simplification generally. There are five different CGT rates which could apply for an individual realising a capital gain – 0%/10%/18%/20%/28%. There is a good argument to say that there should be a single flat rate of CGT.”

What is CGT?

CGT is a tax on the profit when you sell an asset that’s increased in value. The tax is only payable on gains above your annual tax-free allowance which is currently £12,300.

If you’re a basic rate taxpayer, the rate you pay depends on the size of your gain, your taxable income and whether your gain is from residential property or other assets.

If you’re a higher or additional rate taxpayer you’ll pay 28% on your gains from residential property and 20% on your gains from other chargeable assets. However, you only pay CGT on the sale of second homes, not your main residence.

Any CGT hike would impact wealthy households the most.