Andersen, the embattled accounting firm, faces a tough uphill struggle trying to persuade competition authorities around the world to allow its proposed merger with KPMG outside the US to go ahead, according to bankers and competition lawyers.

Andersen has confirmed that it is in talks to merger its business outside the US with KPMG, a move that would reduce the Top Five global accounting firms to four. Such a deal is seen as the last chance to avoid a break-up of Andersen's global network in the wake of Andersen's role in the Enron collapse.