Bidding to lead his Conservative Party back to power in a May 6 election shaping up to be a tight race, Cameron also sought to press home what he sees as his advantage on economic policy, insisting his plans to cut public spending were solid.

The Conservatives are ahead in the polls but not by a big enough margin to be sure of winning an overall majority in parliament. If they fall short of that goal, a variety of outcomes are possible including another Labour government.

To avert that scenario, Cameron needs to broaden his appeal beyond the traditional right-leaning, affluent, rural or suburban core Conservative electorate and that was what he sought to do by promising a public sector "fair pay review.”

"There's a real problem here which is the public sector and the private sector sort of chase each other's tail in endlessly increasing top people's pay," he said in a BBC radio interview, describing current pay inequalities as "outrageous.”

"We're saying this roundabout needs to stop and let's start with the public sector and say ... bosses shouldn't be paid more than 20 times more than the people who are paid the least." The comment sought to tap into a public mood of resentment against high earners, particularly in the financial services industry, after a recession that has seen hundreds of thousands lose their jobs or have to accept pay freezes or cuts.

It was also part of Cameron's strategy to change an old perception, dating back to Margaret Thatcher's days as prime minister in the 1980s, that Conservatives stood for the interests of the rich and didn't care much about inequality.

"There has been a strange reversal in British politics. Labour have become a reactionary force while the Conservatives are today the radicals," he wrote in a column published in Friday's Guardian, a newspaper much more sympathetic to Labour.

In a direct appeal, he wrote: "To Guardian readers everywhere, I say: overcome any prejudices you may have." EFFICIENCY SAVINGS The parties clashed again over how and when to tackle a 167-billion-pound ($255 billion) budget deficit weighing on investor confidence and threatening Britain's triple-A credit rating.

Labour has pledged to halve the deficit within four years, but says cutting public spending now would endanger a fragile recovery. It plans to increase a payroll tax, National Insurance, to raise money to service the debt.

The Conservatives counter that they would reduce public spending immediately, and say the National Insurance hike is a tax on jobs that would itself threaten the recovery. They back a more limited rise that would exempt seven out of 10 workers.

Labour has been placed in a tight spot this week as dozens of business leaders have come out in support of the Conservative stance. Prime Minister Gordon Brown drew fire for saying that the bosses were "deceived" by unrealistic Conservative pledges.

Cameron sought on Friday to press home the issue, reiterating that the Conservatives had "doable, deliverable" plans to pay for scrapping part of the National Insurance rise through "efficiency savings.”

"All these claims that Labour have been making that it is not deliverable to save 12 billion pounds ($18 billion) gross, 6 billion pounds net in the first year of Conservative government simply are not right," he said in his radio interview.

A former government adviser now working for Cameron, Peter Gershon, told the Financial Times the savings would come from not filling public sector vacancies, cutting spending on IT, consultants and staff expenses, and renegotiating contracts.