Mark Perkins, the newly-appointed head of the combined Prebon Yamane and Tullett brokerages in the US, has left the firm, according to sources close to the company.

It is the second top-level US management exit to hit the firm since Prebon was taken over by Collins Stewart Tullett in October. Keith Miles, the former head of Prebon US, is understood to have been made redundant in the wake of the takeover.