Royal Bank of Scotland and Mizuho have agreed to swap £175m of debt for equity in 20:20 Mobile, the struggling mobile phone distributor, in return for its private equity owner Doughty Hanson injecting an extra £15m.

The debt restructuring is the latest example of a private equity group being forced to plough more money into a troubled investment to win some room for manoeuvre from banks and to cut debt from unsustainable levels.