Greenpeace and CND claimed that 600 people invaded the grounds of the Prime Minister's official country residence, just before Jacques Chirac, the French President, arrived to meet John Major.
France carried out its third nuclear test on Friday under Mururoa Atoll in the Pacific Ocean and Greenpeace has launched a campaign to disrupt the President's two-day visit.
Janet Cronvery, spokeswoman for Greenpeace, said: "Jacques Chirac wouldn't have dared to carry out a test on the eve of a visit to any other country but he knew he could rely on John Major's support. John Major is the only leader in the world he can rely on over nuclear testing."
Martin Jones, CND's vice- chairman, said: "Those arrested crossed the perimeter fence with the intention of joining in the summit meeting. We believe that they better represent public opinion than either head of state."
Campaigners will also gather outside the Foreign Office today, where Mr Chirac will continue his series of meetings with Mr Major.
Greenpeace spent several days planning yesterday's demonstration. The protesters gathered secretly in the woods and hills surrounding Chequers while CND held a demonstration near the main gates.
Two hours before President Chirac was thought likely to arrive, a group of 150 people wearing red, white and blue Greenpeace boiler suits and waving flags proclaiming "Non" swept down a hillside to the north-west of Chequers. Hundreds of police ran to intercept them. Another 150 then ran from the south-west and then the police were forced to split their numbers to try and prevent them from reaching Chequers. Three hundred then ran through the middle of the police lines and approached within 100 yards of the country retreat. Eventually the protesters approached within 15 feet of a hedge that surrounds the house.The police made 12 arrests and set up roadblocks.Reuse content