Large companies that allow their highest paid employees to reduce the amount of tax they pay on big bonus pay-outs, should be compelled to reveal the details, a champion of good corporate governance, has urged.

PIRC, the independent research and advisory consultancy providing services to institutional investors on corporate governance and corporate social responsibility issues, has contacted a number of remuneration consultants used by companies, to see if they encouraged their clients to exploit the cut in the top rate of income tax on 6 April.

The Guardian report follows on from revelations that insurer Aon approved 250 of its highest paid staff to defer bonuses to the beginning of the new tax year in order to benefit from the tax rate falling from 50% to 45%.

PIRC- which advises pension funds, faith-based investors, trade unions to banks and asset managers - said it wants to know if any businesses have acted on advice by remuneration consultants to defer payments into the new tax year and if the remuneration firms have brought in any such changes for their own staff.

PIRC suggests that where deferrals have been made, that information should be revealed in the company annual report.

Investment bank Goldman Sachs decided against its plans to deny the taxman millions of pounds by shifting the date on which it pays out its bonuses.

Senior figures at the bank decided against the controversial scheme only after Bank of England governor Sir Mervyn King said it would be 'depressing' and 'lacking in care and attention' to the rest of society, reeling from the double-dip recession.

Many firms are believed to have considered deferring payments into the New Year after the chancellor announced the tax cut in his last Budget.