Strong first-half results at Barclays’ corporate and investment bank were overshadowed by revelations of a new regulatory probe into the UK bank and four past and present senior staff, including its finance director.

The UK bank, which has already been the subject of public anger over its role in the fixing of Libor, revealed in its first half interim report this morning that it was under investigation by the UK regulator over whether it had provided sufficient disclosure during capital raisings carried out in late 2008.