The Office of Rail Regulation (ORR) has slimmed down its legal panel to three firms in the latest shake-up of its core advisers.

Berwin Leighton Paisner and Shearman & Sterling have both been dropped from the updated panel, after a review led by ORR director of legal services Juliet Lazarus.

Norton Rose has kept its place on the roster, having originally been appointed in 2002 and reappointed in 2005. Joining the top 10 City firm are London boutique Ingram Winter Green and IP/IT specialist firm Waterfront Solicitors.

Norton Rose's reappointment took effect from 1 July, while the other two firms began their new tenure as of 1 September. The appointments will last for five years.

The ORR, an independent safety and economic regulator for British railway networks, has an annual external legal spend of around £400,000.

Michael Grenfell, ORR relationship partner at Norton Rose, said: "We are thrilled to have been appointed for the next five years as a preferred supplier of legal services to the ORR following a thorough evaluation."

"We welcome this as a recognition of the experience and expertise we can offer, and we will endeavour to justify the ORR's decision by providing the ORR with a high standard of service over the coming years."