Ashurst is advising Royal Mail as it prepares to appeal against communications regulator Ofcom's decision to fine the company £50m for breaking competition law.

Royal Mail was handed the fine after the regulator upheld a complaint by the mail transportation company's wholesale customer Whistl.

Whistl – which when the complaint was raised in 2014 was known as TNT – accused Royal Mail of changing wholesale customers' contracts and introducing price increases, at a time when Whistl was seeking to compete directly with Royal Mail on the delivery of bulk mail.

Ofcom "found Royal Mail's actions amounted to anti-competitive discrimination against customers, such as Whistl, who sought to deliver bulk mail".

Ashurst competition and antitrust partner Nigel Parr has been leading the firm's team, which also includes competition partner Duncan Liddell, throughout the process. The firm instructed Monckton Chambers' Daniel Beard QC, Robert Palmer and Ligia Osepciu on Royal Mail's behalf.

Royal Mail said earlier today that it would appeal the decision, adding that it was "very disappointed" by Ofcom's decision to impose the fine, calling it "fundamentally flawed".

The company will not pay the fine until the appeal process, which it expects to launch within the next two months, is complete.

London law firm Towerhouse is advising Whistl, with partner Rosaleen Hubbard leading. The firm has instructed Mockton Chambers' Alan Bates.

Jonathan Oxley, Ofcom's competition group director, said: "Royal Mail broke the law by abusing its dominant position in bulk mail delivery. All companies must play by the rules. Royal Mail's behaviour was unacceptable and it denied postal users the potential benefits that come from effective competition."