PHILADELPHIA – Bill Cosby’s lead criminal lawyer in Pennsylvania is fighting a subpoena related to his $2,500 donation to the ex-prosecutor who says he had promised Cosby that he would never be charged.

Lawyer Brian McMonagle co-hosted a political fundraiser for former District Attorney Bruce Castor early last year but said it took place months before he joined Cosby’s defence team in September.

Castor declined to charge Cosby in 2005 after Andrea Constand accused the actor of drugging and molesting her. She recently sued Castor for defamation over his comments that she has changed her story about the encounter.

Her lawyer now wants McMonagle to detail any ties between his office and Castor, including phone records and documents. She wants Cosby to do the same.

Cosby’s civil lawyers, seeking to quash the subpoena, called the requests “a blatant attempt to disrupt Mr. Cosby’s criminal defence and harass his attorney.” They said that McMonagle’s donation to Castor’s campaign has nothing to do with the defamation case against Cosby.

“He should not be forced to turn over his client’s confidential information and be dragged into this lawsuit at the whim of Constand’s attorneys,” lawyer Samuel Silver and others wrote in a filing Thursday.

Constand’s lawyer, Dolores Troiani, declined to comment Friday on her need for the information.

Castor lost the race for district attorney to career prosecutor Kevin Steele, who went on to arrest Cosby in December.

Castor later sided with the defence in testifying that he had promised that Cosby would never be charged over Constand’s complaint. A judge found no evidence of such a deal and refused to dismiss the case, although Cosby’s lawyers have appealed.

A hearing on pretrial motions in Constand’s defamation case is set for April 15.

Cosby remains free on $1 million bail in the criminal case, which is on hold amid the appeal.