One of Britain's most senior Roman Catholics has accused David Cameron of ignoring the poor while protecting his "very rich colleagues" in the City.

Cardinal Keith O'Brien, the head of the Catholic church in Scotland, said it was "immoral" how the less well-off had been made to "suffer" for the failings in the financial services sector.

In an interview with BBC One's Sunday Politics in Scotland, he urged the Prime Minister to introduce a "Robin Hood tax" on financial transactions to raise money for the poor.

Mr Cameron is opposed to unilateral action on a financial transactions levy and described plans for an EU-wide scheme as "madness".

But Cardinal O'Brien said: "My message to David Cameron, as the head of our Government, is to seriously think again about this Robin Hood tax, the tax to help the poor by taking a little bit from the rich.

"The poor have suffered tremendously from the financial disasters of recent years and nothing, really, has been done by the very rich people to help them.

"And I am saying to the Prime Minister, 'look, don't just protect your very rich colleagues in the financial industry, consider the moral obligation to help the poor of our country'."

The Cardinal said he was not only concerned about people in "abject poverty" but also people who might have thought themselves "reasonably well-off".

A Downing Street spokesman said: "The Government inherited enormous debt but the Prime Minister is determined to help people who are struggling with the consequences of that.

"That's why the last Budget took two million people on the lowest incomes out of tax altogether and from April 2012 pensioners will see the largest ever cash rise in the basic state pension."