Prime minister David Cameron has signalled his intention to extend his “big tent” government beyond the Conservative/Liberal Democrat coalition, talking to Labour MP Frank Field about poverty and appointing left-leaning economist Will Hutton to head an inquiry into public sector pay.

Mr Field this morning confirmed that he had spoken to Mr Cameron about the terms of reference of a new poverty commission, but played down reports that he was to be appointed the new government’s anti-poverty tsar.

Mr Cameron said that Mr Hutton - a vice-chair of the Work Foundation and former Observer editor whose work was influential on the early years of Tony Blair’s government - will lead a fair pay review for the public sector.

“The idea is to improve fairness in the public sector and say that, between the lowest paid and highest paid in the public sector, there shouldn’t be a difference of more than 20 times,” the prime minister told BBC1’s Andrew Marr Show.

He made clear that the BBC would be excluded from the review, but said it would cover NHS managers and senior Whitehall mandarins.

“If you take some of the current organisations, the differences between the top pay and the lowest pay are something like 25, 30 times. I’m afraid to say in the BBC it’s more like 50,” said Mr Cameron.

“I think it’s wrong that in the public sector we have such high pay differentials and I think we can lead by example. It’s a classic example of how we can make the country fairer at the same time as cutting the public deficit.

“In any organisation in the public sector, the highest paid shouldn’t be paid more than 20 times the lowest paid. It may mean lifting the lowest paid, it may mean reducing the pay of the highest paid, but it will make our country and our public services fairer.”