(Reuters) – The CEO of an independent British oil producer which is buying North Sea assets owned by Shell and Exxon Mobil is being sued by his former employer for allegedly forging documents to steal substantial sums.

Viaro Energy CEO Francesco Mazzagatti is accused by Singapore-based company Alliance Petrochemical Investment of being involved in the misappropriation of at least 143.8 million euros ($151.5 million), court filings show.

The lawsuit, which was first reported by the Financial Times newspaper, was filed at London’s High Court in August.

Mazzagatti, who was previously chief executive of Alliance Petrochemical Investment, denies the allegations and he and his co-defendant, Francesco Dixit Dominus, Viaro’s finance chief, in their written defence deny misappropriating any funds.

Viaro Energy did not immediately respond to a request for comment.

Viaro Energy said in July that it would buy Shell and Exxon’s Southern North Sea assets and assume full ownership of one of the largest and longest producing gas asset portfolios on the UK Continental Shelf, subject to regulatory approval.

Viaro acquired RockRose Energy in 2020 and since then has made several other deals in the British and Dutch North Sea. The company produces around 30,000 barrels of oil equivalent per day and has interests in over 30 fields, according to its website.

Alliance Petrochemical Investment alleges in its lawsuit that “there is credible evidence to suggest that Mr Mazzagatti used at least part of the misappropriated funds to acquire a majority share in RockRose Energy”.

Mazzagatti and Dixit Dominus denied that allegation in their written defence. They also say the allegations are the subject of separate litigation in England and Italy, which the defendants are also defending.

(Reporting by Sam Tobin; additional reporting by Ron Bousso; editing by Jason Neely)