Macquarie Group is to sell its in-house margin lending operation six months after it began winding down its residential mortgage business that had also fallen victim to the higher cost of debt since the credit crisis began last year.

As a single A rated bank, it costs Macquarie more to raise debt than Australia’s four large retail banks, which are all double A rated. Commonwealth Bank of Australia, Westpac and St George account for close to 60 per cent of Australia’s margin lending business.