PARIS, Nov 29 (Reuters) - France is prepared to talk to Britain about migration if it is ready for serious discussions, interior minister Gerald Darmanin said on Monday, as he urged the UK to "limit" its economic attractiveness to migrants. Darmanin also told a news conference that Prime Minister Jean Castex will write to British Prime Minister Boris Johnson on Tuesday to detail French demands. "The French government is prepared to resume talks with British authorities if there is no longer double speak"," Darmanin said. The two countries - already at loggerheads over post-Brexit arrangements - have accused each other of not doing enough to manage migration after 27 people died on Wednesday trying to cross the Channel. Amid a growing rift, France cancelled an invitation to British Interior Minister Priti Patel to attend a meeting on Sunday with European counterparts to discuss the situation. Asked about Britain"s proposal of joint patrols to prevent more boats from leaving French beaches, Darmanin said: "Can you imagine French policemen on British beaches? We are not the subcontractors of the British government." "The main issue of the attractiveness of the UK is without doubt the main reason of the situation that we face," he added.