Pinsent Masons is on the receiving end of an £18m negligence claim following advice it gave to trustees of a pension fund in 1998.
The Court of Appeal rejected Pinsents' appeal last week on a preliminary issue in the case, which is due to go to the High Court next January.
Capital Cranfield Trustees brought the claim against Pinsents forerunner Pinsent Curtis, alleging its advice resulted in a £10m deficit to the pension scheme of K&J Holdings.
In 1997, the company gave the trustees six months' notice that it wanted to terminate the scheme. Shortly before the scheme's termination date, Pinsents advised that the trustees did not have the power to demand a contribution from the company to make the scheme fully funded.
On the preliminary issue, Pinsents claimed that, under the rules of the pension scheme, no such contribution would have been permitted. In a December 2004 decision, Mr Justice Lindsay disagreed.
On 13 July, the Court of Appeal upheld Lindsay J's decision.
The decision paves the way for a full trial next year. That will deal with issues of liability and quantum. Capital Cranfield is claiming around £18m from the firm.
Capital Cranfield instructed Katherine Denny of Sacker & Partners, with Outer Temple Chambers' Nigel Inglis-Jones QC and Nicolas Stallworthy as counsel. Pinsents instructed Lovells partner Angela Dimsdale Gill, who used Alan Steinfeld QC of XXIV Old Buildings.
A Pinsents spokesperson insisted that the firm was defending the case vigorously and declined to comment further.