Earlier this month, business secretary Vince Cable warned the government’s majority stake in the bailed-out bank may not be sold for another five years and ratings agency Fitch suggested a split was unlikely.

In a letter to the Financial Times on Monday, Parliamentary Commission on Banking Standards chairman Andrew Tyrie said the future structure of RBS was a matter of urgency.

Splitting the ‘bad assets’ from the good ones within RBS would not affect the underlying position of the economy, he argued, and taxpayers might be better off because of the split:

“Formal accounting conventions should not be allowed to get in the way of what is best for the economy in general and the SME sector, for whom bank finance is particularly important.

“From this work we should soon get to the point where RBS is playing a full role in supporting the economy, and much sooner than would otherwise be the case.”

Speaking soon after the commission called for a break-up of RBS in its June report, the Chancellor George Osborne said the split was possible but a sale was some way off.

He is expected to decide the future of the bank in the autumn.