Gordon Ramsay’s father-in-law and two of his brothers-in-law have admitted hacking computers at the celebrity chef’s restaurant and business empire during a time of bitter dispute in the family.

Chris Hutcheson and two of his sons – Adam and Chris Jr – pleaded guilty at the Old Bailey on Tuesday to charges of conspiring to cause a computer to access programmes and data without authority.

Hutcheson, 68, the father of Ramsay’s wife, Tana, and his sons hacked the computer system at Gordon Ramsay Holdings between 23 October 2010 and 31 March 2011. Hutcheson’s daughter, Orlanda Butland, denied the charge but the prosecution offered no evidence in her case, in effect withdrawing proceedings.

In October 2010, Hutcheson was sacked by Ramsay as chief executive of Gordon Ramsay Holdings. The following year the pair ended up in a high court battle, with Ramsay alleging his computers had been hacked and blaming Hutcheson amid claims that emails between Ramsay and Tana had been read by a third party.

The Hutchesons were charged under Operation Tuleta, one of several investigations that followed revelations of phone hacking involving the media. Its main focus was the illegal interception of messages on computers, which can be done in several ways, including the installation of spyware.

The judge, Gerald Gordon, adjourned sentencing to 2 June. The defendants were released on bail and face a maximum possible sentence of two years in prison.

The court heard Hutcheson was due to go into hospital this month for a hip replacement operation.

Hutcheson has a home in Druillat, France, but gave his address as Earlsfield, south-west London. Chris Hutcheson Jnr, 37, lives in Welwyn Garden City, Hertfordshire, and Adam Hutcheson, 46, lives in Sevenoaks, Kent.

Ramsay has restaurants around the world and a television career in the UK and US. Famed for his short temper and prolific swearing, his businesses ran into trouble after years of expansion. They have since been restructured and Hutcheson’s interests were bought out by Ramsay in order to sever all ties after the court wrangle and family feud.

Ramsay and Tana married in 1996 and have four children.