Credit Suisse Group AG is facing another allegation of spying, this time from a former executive at a joint venture owned by the bank.

Colleen Graham claimed she was followed by a woman over the course of three days in July 2017, alleging it was in retaliation over a dispute regarding an accounting matter at the joint venture Signac, The Wall Street Journal reported, citing U.S. labor court filings.

Graham has been with Credit Suisse for 20 years and served as its compliance head for the Americas before being named co-head of Signac, which was set up in 2016 to catch bad behavior by rogue traders through data analysis. She was not an employee of Credit Suisse at the time of the purported surveillance.

Following reports in September of the spying of the bank's former wealth management head Iqbal Khan, Graham emailed Credit Suisse CEO Tidjane Thiam, Chairman Urs Rohner and another board member detailing her alleged surveillance, and asked the Swiss lender to investigate the matter and to pass on her information with regulators and the law firm investigating Khan's case, emails reviewed by the Journal showed.

Graham also met with Swiss financial regulator Finma in November to discuss her allegations, a person familiar with the matter told the Journal.

She previously notified Credit Suisse of the alleged surveillance in a whistleblowing complaint against the bank and U.S.-based data mining company Palantir Technologies Inc., its co-partner at Signac. Graham claimed the firms pressured her in 2017 to manipulate Signa's accounts so it could book certain revenue for 2016 and received "thinly veiled threats" after refusing to do so, according to the report.

The U.S. Labor Department's administrative court is expected to hear the whistleblowing case in early 2020.

A spokeswoman for Credit Suisse said the lender had carried out thorough investigations into her claims and concluded that they were baseless, the report noted.