Freshfields Bruckhaus Deringer has won itself a new Ftse 100 client after being appointed primary corporate adviser at mobile phone giant mmO2.

The appointment follows mmO2′s demerger from BT last month and represents the start of a major review of external advisers at the company, which is looking to appoint a raft of new firms.

The 50-strong in-house department, under the leadership of general counsel Philip Bramwell, is looking to put together a roster of five firms to handle work in a range of disciplines.

Confirming Freshfields' appointment as primary corporate advisers, Bramwell said the firm advised the division on its demerger opposite BT's main adviser Linklaters and it made sense to retain Freshfields on a long-term basis.

Linklaters is continuing as BT Group's primary adviser, although the break up of the monolith will inevitably dilute the amount of work it receives.

Shearman & Sterling has been appointed as mmO2′s US adviser.

Bramwell also confirmed that the break-up of BT's 150-plus legal team, 50 of whom joined mmO2, would lead to more work for outside lawyers.

He said: "We are leanly staffed so we will outsource more work than before and we need a broader range of firms than we did when we were part of BT."

Bramwell added: "It is all about individuals and we want to build a series of relationships with individuals and their firms. We are looking for the best performance and the best cost."

He confirmed that the company is in talks with a number of firms, some of which acted for the mobile operator prior to the demerger, with a view to building relationships with "the best, leanest and hungriest".

BT's in-house trademark attorneys will continue to work with mmO2.

Bramwell also confirmed that the intellectual property dispute over the £1m rebranding of mmO2 and the O2 trade name, has progressed to court proceedings.

Burford, the owner of a North London shopping centre called O2, has issued a claim against the mobile operator in relation to the branding.