Duke Street Capital, the private equity group, has paid £8m ($14m) to top up the Focus DIY pension fund a year after selling the struggling home improvement chain to Cerberus Capital Management.

The payment by Duke Street, which sold Focus DIY last year in a £225m deal valuing it at less than its debt, is the first case of the pensions regulator making a private equity firm retrospectively responsible for pensions at a company that it has sold.