The Financial Conduct Authority (FCA) has appointed two outside firms to investigate Royal Bank of Scotland’s treatment of business customers after a government adviser accused the bank of driving small enterprises into administration. The City regulator said it had chosen Promontory Financial Group and Mazars to carry out an independent report on RBS, which is 81% owned by the government. Promontory advises companies on risk and regulation and Mazars is an accountancy firm with a specialist banking practice. The firms will examine RBS’s treatment of businesses in financial difficulty and consider allegations of unfair practice made by Lawrence Tomlinson in November. Tomlinson is an adviser on entrepreneurship to the business secretary, Vince Cable. Tomlinson alleged that the bailed-out bank moved commercial borrowers whose property had fallen in price into its global restructuring group, where they paid management fees and higher interest. Companies that subsequently collapsed then had their properties bought by RBS’s distressed debt unit, West Register, Tomlinson alleged. RBS has said the allegations are unproven but have been very damaging. The first stage of the review will consider RBS’s treatment of a sample of customers referred to the global restructuring group. It will include some cases where customers have raised concerns with Tomlinson, Cable’s department or the FCA. The review will also judge whether any bad practice identified is widespread within RBS and systematic. If so, the review will look for the problems and make recommendations to stop them.