Mr Ramsay, who was head chef of the double Michelin-starred London restaurant L'Aubergine, and Marcus Wareing, who was head chef at L'Oranger, also in London, are being sued over a dispute in which staff quit and police were called to investigate claims of theft and sabotage.
Yesterday Mr Ramsay, a former Glasgow Rangers footballer, and Mr Wareing said that they would fight the action vigorously.
In the High Court writ issued by A-Z Restaurants, which owns both premises, the two are accused of involvement in pounds 30,000 of alleged sabotage to L'Oranger in a night-time raid.
The writ said that wires in the pastry oven were tampered with, endangering anyone who tried to use it, refrigerators were turned off, destroying food inside, and knobs and rings were stolen from a stove.
It also claimed that pages were torn from the reservations book and stolen early on 19 July, the day after Mr Wareing was dismissed because of a soaring wage bill and a "truculent and unco-operative attitude" to his bosses.
Mr Ramsay is alleged to have returned to L'Aubergine and encouraged staff to resign. Thirty-nine left, leaving one behind, the company claims. Both restaurants had to close and L'Aubergine only reopened on 10 September but the takings have remained down.
Mr Ramsay, 32, was also accused in the writ of intimidating the pastry chef at L'Oranger and threatened that "they would break him" if he did not resign.
A-Z said that both restaurants had suffered a substantial loss of profits and considerable damage to their reputations among their celebrity clientele, which includes Princess Margaret, Robert De Niro and Sean Connery.
Giuliano Lotto, co-director of A-Z, said yesterday: "We are looking at a substantial amount of money, somewhere between pounds 500,000 and pounds 1 million."
He added that he had got on well with Mr Ramsay and believed he was ready to seal a four-year consultancy deal with him, but instead the chef walked out.
"Mr Ramsay led me up the garden path. We set up Mr Ramsay: he was not known to the world four years ago," he said. "He is a very capable and talented chef - that goes without saying - but the stage for him to perform was supplied by us."Reuse content