LONDON - Sterling slipped to a session low against the U.S. dollar on Wednesday after the release of a report by a senior civil servant into lockdown breaches at British Prime Minister Boris Johnson's Downing Street office.

A failure of leadership was to a blame for a culture that led to illegal parties being held during coronavirus lockdowns, the report by senior official Sue Gray said.

Sterling was down 0.4% to a session low of $1.24855. Against the euro, the pound was up 0.3% at 85.40 pence but off session highs.

"The senior leadership at the centre, both political and official, must bear responsibility for this culture," the report said. "Many of these events should not have been allowed to happen."

(Reporting by Samuel Indyk; editing by Dhara Ranasinghe)