British Prime Minister David Cameron's flagship gay marriage policy deepened a rift in his own party on Monday after many of his own lawmakers defied him in a sign of growing strains on his leadership and his coalition government. Almost 40 percent of Cameron's 303 lawmakers in the lower house of parliament voted for an ultimately unsuccessful amendment that would have allowed registrars to refuse to perform gay marriage ceremonies if they objected. Scores backed another amendment that the government said would have sabotaged its efforts to legalize same sex unions. Cameron's failure to unite his ruling Conservative Party over gay marriage and over his other major policy - renegotiating Britain's membership of the European Union - risks undermining his chances of being re-elected in 2015 even as the economy is showing signs of returning to growth. "It's a perfect political storm. It couldn't have come at a worse time for Cameron," Iain Dale, a