Freshfields Bruckhaus Deringer has hired a new external adviser as the alleged tax scandal relating to so-called 'cum-ex' transactions continues to be investigated by German authorities.

The Magic Circle firm has turned to criminal law specialist Florian Ufer, who is known for advising board members and senior executives on investigations including Deutsche Bank cases and Volkswagen's fuel emissions controversy. He is a partner at the Munich base of law firm Ufer Knauer.

Ufer replaces Daniel Krause of Krause Kollegen who was previously advising the firm, according to a person with knowledge of the situation.

A spokesperson for Freshfields said: "We can confirm that we chose to mandate a new external adviser. We are currently discussing with him the next steps."

The change highlights the seriousness with which Freshfields is taking the investigation, which saw its former head of international tax Ulf Johannemann arrested last week.

The transactions were allegedly used by a number of banks to claim multiple refunds of tax that had only been paid to the German authorities once, before a loophole allowing such practices was closed in 2012.

Earlier this year, Freshfields was sued for €95 million over advice it gave to the German arm of Canadian-headquartered Maple Bank regarding the issue. Maple Bank later collapsed when its financial position became unstable after it had to pay back unpaid taxes.

The wider scandal has been investigated by German authorities for several years, with the Magic Circle's Frankfurt base being raided three times in relation to the issue.

Meanwhile, a spokesperson for the German Federal Ministry of Finance said its stance remains that the cum-ex transactions are "illegal", adding it is now for the "competent law enforcement authorities to investigate the alleged criminal charges", while adding that tax authorities are still conducting investigations.