High earners, wealthy investors and landlords are set to fall under greater scrutiny following sweeping changes to tax rules proposed by the government last week.

The Revenue is seeking extraordinary powers that would, if granted, compel accountants to disclose the names and addresses of clients who take up schemes to avoid the top rate of income tax, which is due to increase to 50% in April next year.

The spotlight will also fall on thousands of landlords after the taxman proposed measures to force lettings agents to reveal details of all previous clients.

Under current rules, the Revenue can only ask lettings agents to disclose landlords for whom they currently collect rent. It is now seeking to extend its powers to agencies that have introduced a tenant to a landlord for a fee in the past, even if rent is now paid directly to the landlords. The Revenue estimates that 10% of landlords who use lettings agents do so on an introduction-only basis.

“A power that included such transactions and the addresses they relate to would allow HMRC to make sure that people with income from letting property pay the right tax,” the Revenue said.

Peter Bolton King of the UK Association of Letting Agents, said: “While this push by the Revenue has the potential to catch a lot more landlords out, it will also create a lot more work for agents in terms of their record keeping.”

The proposed crackdown will also hit higher earners seeking to avoid 50% tax — or 51.5% with National Insurance contributions included.

Last week, The Sunday Times revealed that Grant Thornton, the accountant, has been marketing a scheme to bankers and hedge-fund employees to beat the 50% tax rate. It would allow workers to take a specified amount of share options in lieu of a cash bonus, on which they would pay capital-gains tax (CGT) rather than income tax.

However, the Revenue is seeking a “new specialist information power,” according to documents on its website last week. This would allow it to demand that accountants reveal the names and addresses of all individuals using such schemes.

John Whiting of the Chartered Institute of Taxation, said: “It is one thing to ask accountants to tell them about schemes, but they want to know who’s using them too. The Revenue can then see if it is going to a lot of people and, depending on the sort of people it is going to, this will help the Revenue decide if they should block it.”

The consultation on the new powers ends in October, so they could be in force for the new tax year. The Revenue will also have “blacklist” powers from next April, to coincide with the end of the second amnesty for offshore account holders which will run from September to March.

Both offshore taxpayers and landlords could find themselves on the blacklist if they have understated their tax by £25,000 or more.

Buy-to-let landlords are being urged to come forward if they have undisclosed rental income. A Revenue spokesman said: “This will help mitigate penalties which may apply to those who have unpaid tax in the past.”

If you have rental income of £1,000 a month but your interest repayments are £800, you would be liable for tax on only £200, assuming you make no other deductions.