Chadbourne & Parke has delivered a stinging response to a $100m (£80m) gender discrimination suit filed by two former female partners.

In its 62-page retort, the US firm lashed out at Kerrie Campbell, a litigator hired by the firm in January 2014, calling her a dishonest partner who failed to live up to her promises to the firm and embarrassed it before clients.

Campbell, who fired the first salvo against Chadbourne with her complaint on 31 August, claimed in court papers to have filed her case on behalf of 26 current and former female partners. In October, former Kiev office managing partner Jaroslawa Zelinsky Johnson joined Campbell as a name plaintiff in the case.

Chadbourne has publicly called Campbell's claims entirely without merit and, in the firm's lengthy response to her allegations, maintained that it tried to appease an individual who "blatantly mis-stated" her compensation arrangements with the firm, did not generate anywhere near the revenue necessary to place Campbell within a class of high earning partners and "sought to claim ordinary client expense reimbursements as fee revenue generated by her".

Chadbourne claims that partner Abbe Lowell, the head of the firm's litigation department who was named in an amended complaint filed by Campbell on 27 October, was responsible for handling a "defamation matter for a high net worth individual" that Campbell brought to the firm as a client. Chadbourne alleges that the individual, who it does not name, was dissatisfied with Campbell's previous work and requested that she not work on the matter. Lowell instead took the lead on the engagement, which Chadbourne claims is responsible for $1.522m (£1.2m) of the $2.155m (£1.7m) in billings that Campbell took credit for in 2014.

Chadbourne also alleges that Campbell was difficult for associates in the firm's litigation department to work with and that she "exhibited questionable legal judgement". Chadbourne states that Campbell's "wasteful use of associate time led to a number of write-offs". The firm also claims that on at least one occasion, a Chadbourne lawyer approached management with concerns that "he would be subject to sanctions had he advocated for Campbell's position" in a client matter.

Campbell also arrived at a firm event "already inebriated", acted in a "shocking and inappropriate manner toward the male fiance of a male Chadbourne attorney", and made "graphic comments" to a male lawyer at the same event, according to the firm's response.

During an out-of-town trial – Campbell is based in Washington DC – the firm alleges that she again "displayed poor judgment with respect to the use of alcohol in the presence of a client between trial days".

With regard to an alleged videotape of Lowell rearranging items in Campbell's office mentioned in her amended complaint, the firm claims that he was merely removing items he observed as "being inappropriate for a professional environment", not knowing whether they were placed there by Campbell or someone else. In removing such items, Chadbourne acknowledges that Lowell may have taken down a "card with a Nelson Mandela quote" that Campbell cited in her amended complaint. The firm states that Campbell recorded these acts of "office management" – not relation against her for suing the firm – via a secret camera.

As for Johnson, the former head of Chadbourne's Kiev office who spoke with The American Lawyer last month about her decision to join Campbell's case, the firm acknowledges that she was a respected leader of its outpost in Ukraine, "the economics of which were challenging and affected her compensation". Chadbourne said it closed its Kiev office as a result of Ukraine's "difficult political and economic circumstances" and Johnson "returned to Illinois after resigning her partnership".

Chadbourne also filed a counterclaim against Campbell for breaching her fiduciary duty to the firm by including confidential financial information in her court filings and embarking on a public campaign of "knowingly false statements" that harmed Chadbourne's reputation. The firm, which seeks monetary and punitive damages from Campbell, also accuses her lawyer, Sanford Heisler's David Sanford, of taking an aggressive position in the press in order to further his interests in cases against other potential defendants.

"The true goals of Sanford and Sanford Heisler are to make an example of how they are able to inflict injury upon Chadbourne reputationally, and thereby to serve notice to other law firms or companies that, should a future complaint arise against them, they would be well served to settle with [Sanford] 'at the front end' or they, too, would be subject to a baseless nationwide smear campaign of falsehoods like the one now being conducted against Chadbourne," the firm said in its response and counterclaim.

Proskauer Rose employment litigation partner Kathleen McKenna is leading a team from the firm representing Chadbourne on the case. McKenna previously worked with Dechert in advising her own firm on a $10m (£8m) gender discrimination dispute with former CFO Elly Rosenthal.

Sanford represented Rosenthal, who settled her case against Proskauer in 2013. In a conversation last month with The American Lawyer, the chairman and co-founder of Sanford Heisler admitted that he has had settlement negotiations with Chadbourne. Sanford did not respond to a request for comment.