The CBI's president-in-waiting, Roger Carr, has thrown his weight behind the Labour-initiated 50p rate of income tax on Britain's richest earners in a sharp break from the business organisation's vigorous campaign against the policy.

Carr, who was chairman of Cadbury until its takeover by Kraft in February, has raised hopes of a significantly more progressive political approach at the Confederation of British Industry (CBI) by declaring that he supports the top rate of tax as a fair way of spreading the burden at a time of economic hardship.

"My personal view is that when things are difficult, everybody should make a contribution," he said, in an interview with the Observer. "Those who can make a bigger contribution should do so. So I do not think the rate is unreasonable."

The new tax rate is levied on people earning more than £150,000, less than 1% of the population, and is expected to raise £2.4bn a year. It was introduced by former chancellor Alistair Darling and retained in the coalition's finance bill, details of which were published last Thursday.

Carr was named last week as the CBI's next president, to succeed the former Economist publishing boss Helen Alexander in June as head of the organisation that describes itself as the "voice of business". He is chairman of the energy company Centrica, a director of the Bank of England and made his name in the 1980s as the boss of the industrial conglomerate Williams.

His remarks on taxation – which, he stressed, were in a personal capacity – are a sharp contrast to the CBI's official policy. Its former president, BA chairman Martin Broughton, last year condemned the 50p rate as an act of "economic vandalism".

And in a letter to the Treasury ahead of October's comprehensive spending review, the CBI's director general, Richard Lambert, called for an "early commitment to reversing" the new tax band on the grounds that it had "damaged the UK's reputation as a business location".

Carr's softer line on taxing the rich was welcomed by the CBI's traditional opponents. Brendan Barber, general secretary of the TUC, said: "It cannot be right for the very wealthy to demand cuts that will make the lives of the poorest immensely harder while whingeing about having to pay a bit more tax themselves. So it is very refreshing to hear Roger Carr taking a moral stand on the issue. Other senior business people would do well to follow his example."

The tax, attacked by critics as a disincentive to entrepreneurialism, was initially intended to be a temporary measure to bolster the nation's finances. Labour leader Ed Miliband has suggested it should stay but shadow chancellor Alan Johnson has indicated that he sees it as temporary.

Shadow treasury minister Christopher Leslie praised Carr's comments: "It's actually quite a refreshing opinion and I think it probably reflects the views of the majority of the public. When you see spending cuts to so many layers of public services, in terms of tax revenue, it's vital to have a balanced approach."