LONDON (Reuters) - Britain's most senior Roman Catholic cleric resigned on Monday the day after he rejected allegations that he had behaved in an "inappropriate" way with other priests.

"The Holy Father has now decided that my resignation will take effect today, 25 February 2013," Cardinal Keith O'Brien, who had been expected to take part in the conclave to choose the next pope, said in a statement.

O'Brien, who is known for outspoken views on homosexuality, had been reported to the Vatican over allegations of inappropriate behavior stretching back 30 years, according to the Observer newspaper.

O'Brien, the archbishop of St. Andrews and Edinburgh, had rejected the claims.

(Writing by Guy Faulconbridge)