British American Tobacco (BAT) has dropped Linklaters on its investigation into allegations of bribery and corruption, and appointed Slaughter and May as sole adviser on the case.

A spokesperson for BAT said the company had been working with both firms "for some time" on the case, which was triggered by a BBC Panorama documentary in 2015. The spokesperson added: "We have now decided as a matter of efficiency to consolidate the work in one firm, Slaughter and May. We continue to have a strong working relationship with Linklaters in a number of areas."

The BBC documentary found that BAT had paid bribes to officials in east Africa. Since then, US congressmen said additional documents have emerged, which they claim indicate alleged bribery may have been more widespread in Africa.

The company hired Linklaters in February to conduct "a full investigation" into claims made by Paul Hopkins, a former BAT employee. It is not known when it appointed Slaughters and the firm declined to comment.

It is understood Slaughters' team on the deal comprises its London-based co-heads of investigations Jonathan Cotton and Richard Swallow, and investigations partner Damian Taylor.

In October, the London-listed tobacco giant outlined plans for a merger with Reynolds American, the owner of Camel cigarettes, by purchasing the remaining 57% of the US company it does not already own. It instructed Cravath Swaine & Moore and Herbert Smith Freehills to advise on the merger proposal.