White alleged that Withers family partner Marcus Dearle had instructed his ex-wife, Mati, to steal his mail and use it as ammunition in their divorce case.
The celebrity chef is seeking damages for misuse of confidential or private information and wrongful interference with property.
Mr Justice Eady threw out the claim last November ruling: “Even though feelings often run high in the course of matrimonial disputes, that does not justify the making of allegations of criminality, against solicitors or anyone else, without a solid basis for doing so” (20 November 2008).
Withers counsel, 5 Raymond Building’s David Sherborne QC, argued that the claim should be struck out because it was brought only to harass his ex wife.
However, appeal judges Lord Justice Ward, Lord Justice Sedley and Lord Justice Wilson said the case should proceed to full trial.
“It’s not conducive to the administration of justice that such claims are simply swept under the carpet,” their judgment stated.
Sedley LJ conceded that “the desire for vengeance on the lawyers acting for an estranged spouse is as common as it is irrational” and he warned the courts to be wary about “letting such expeditions through their doors”.
But, he added: “If, among these, one turns out to be legally viable, the claimant’s motive cannot shut the court’s door; and this… is such a case.”
Ward LJ added: “It must always be remembered that solicitors are officers of the court and if they’re shown to have done wrong they should face the judgment of the court.”
In a statement Withers said that the Court of Appeal had “simply decided that this complex issue has to be argued fully in court, rather than determined on an expedited basis”.
The firm added: “We’ve always maintained that any allegations made by Marco Pierre White against Marcus Dearle and Withers are completely unfounded.
“It’ll be helpful to family law practitioners and their clients to have the whole issue of disclosure of documents in divorce proceedings considered more fully.”
Hill Dickinson partner Richard Green instructed 3-4 South Square barrister Michael Crystal QC to represent White.
Barlow Lyde & Gilbert instructed Sherborne to represent Withers.