A fee dispute between Nixon Peabody and a former client escalated in San Francisco Superior Court when Judge Marla Miller allowed cross-claims of improper billing against the firm to proceed.

Former Nixon Peabody client Gregory Shenkman, who is represented by lawyers from Cotchett, Pitre & McCarthy, alleges Nixon overestimated the amount he’d recover in a construction defect lawsuit he filed in Marin County in 2009 and made promises about the amount to be billed to him. Shenkman claims the firm told him he’d recover more than $6 million in the action and would pay $360,000 in fees. Instead, Shenkman said in court papers he was billed $620,000 in fees and recovered only a little more than $1 million.

Nixon, represented by Douglas Schwartz of Schwartz & Cera in San Francisco, objected to the cross-claims, arguing Shenkman entered into a fee agreement with the firm and simply stopped paying his bills. The firm sued Shenkman in March to recover $260,000 in unpaid fees.

San Francisco-based Nixon Peabody partner Anthony Barron was counsel on the construction defect case, according to a fee agreement filed with the court.

Shenkman claimed Nixon did not do due diligence or fully evaluate his construction defect claims before estimating recovery and fees, according to court papers filed earlier this month.

In a brief order denying Nixon’s demurrer to Shenkman’s cross-complaint, Miller instructed Shenkman to amend his negligent misrepresentation claim to name the partners who misrepresented the recovery and fees. And she allowed a claim that Nixon reneged on its duty to use the fee money to Shenkman’s benefit.

Camilo Artiga-Purcell, a Cotchett partner who is on Shenkman’s legal team, said last week he is “pleased” with the court’s ruling.

“We believe our client will be vindicated at trial and recover Nixon Peabody’s unconscionable fees,” he said.

Schwartz, who represents Nixon, was not available for comment by deadline, and Barron did not return a message.