Celebrity chef Gordon Ramsay has launched legal action against his wife's family who he plans to sue for millions of dollars, a British newspaper reports.

Ramsay is understood to have filed a writ in the High Court that includes a series of claims against his wife Tana's father Chris Hutcheson, mother, sister, sister-in-law and the father's alleged mistress, British newspaper The Sunday Telegraph reports.

Former CEO of Gordon Ramsay Holdings (GRH), Mr Hutcheson is accused of withdrawing STG1.42 million ($A2.22 million)from the company to fund a double life with a secret second "wife" and family, and paying STG5000 ($A7800) a month to a separate mistress.

The claim further alleges that Mr Hutcheson hacked into the company files thousands of times and put his real wife on the company payroll and wrote five-figure cheques for himself.

The family has been rocked by the news in recent years that Mr Hutcheson had a secret family including two grown-up children, The Telegraph said.

Ramsay once looked to his father-in-law as a mentor, describing the two of them "as alike as two wings on a plane", the newspaper said, adding that in more recent times he has described the older man as "dictator" leading a "very complex life".