£730.5 million paid out in PPI claims in May

This is the largest overall monthly payout to date and pushes the total paid out since January 2011 to £4.8 billion.

But with an estimated £9 billion of compensation due in total, the process still has a long way to go.

In May, Lloyds Banking Group, RBS and HSBC set aside £800 million extra between them, on top of their original pots to pay out from. Barclays set aside an extra £300 million in April.

There has been a huge jump in compensation since the British Bankers' Association trade body ended a legal battle in May 2011 which attempted to block the FSA's rules on compensation.

These rules force banks to review past sales of PPI – to cover loan or credit card payments when people cannot work – and contact mis-sold customers to offer money back, even to borrowers who have never complained.

The most recent figures come from the 24 firms responsible for 96% of complaints about the sale of PPI last year.