A US-style system of top politicians' tax returns being published could be considered in the UK, George Osborne indicated as the issue of personal finances continued to dominate the London mayoral race.

The Chancellor told The Telegraph he was "very happy" for the Government to look at the move and Business Secretary Vince Cable declared that he was prepared to be open about his personal finances.

Pressure for ministers to reveal their income intensified on Thursday when the main rivals competing to become Mayor of London set out details of their own earnings and tax.

The openness was prompted by a bitter public row between Boris Johnson and Ken Livingstone over tit-for-tat accusations of avoiding income tax by channelling earnings through companies.

In an intervention that is sure to open a serious debate, Osborne told the newspaper: "My personal principle has been: make the rules in general more transparent. We are happy to consider publishing tax returns for people seeking the highest offices. Of course, they do it in America."

The developments this week have been seen by many as a sign of an americanisation of British politics.

Osborne also made clear that he would be open about whether he personally benefits in future from the reduction in the top 50p rate of income tax which he controversially cut in last month's budget.

"No doubt, next time I fill in a tax return, I will be asked the question and will give you a straightforward answer," he said - saying he had not been in the top earner category last time.

Backing openness in tax affairs, Cable told The Telegraph: "I'm quite happy to be open about it. I have no problem with my tax return being published while I am in Government."

Livingstone, who is fighting to wrest back for Labour the post he lost in 2008, has come under fire for channelling earnings through a company so that they are liable for corporation not income tax.

In a foul-mouthed bust-up, Tory incumbent Johnson called his City Hall predecessor a "liar" over on-air allegations that he operated a similar arrangement.

Challenged to do so by Mr Livingstone, Johnson and Liberal Democrat hopeful Brian Paddick issued accountant-signed statements of their earnings and tax for the past three or four years.

But although he published some figures, the ex-mayor said he would only give full details of his earnings if others agreed to disclose information concerning spouses and partners.

The figures he did publish were attacked for not making any financial sense, and for lacking the authenticity of an accountants letter, which had accompanied the details released by Johnson and Paddick