MASS murderer Harold Shipman killed up to 15 patients while working as a junior doctor more than 30 years ago, an official report revealed on Thursday.

The deaths occurred between 1971 and 1974 at Pontefract General Infirmary in West Yorkshire, according to the sixth, and final, report of the Shipman Inquiry.

The inquiry has already found that Shipman murdered at least 215 patients with lethal morphine injections while working at a one-man GP practice in Hyde, Greater Manchester, after leaving Pontefract.

Inquiry chairman Dame Janet Smith said that suspicion surrounded a number of other deaths.

In the report - entitled Shipman: The Final Report - Dame Janet said: "My overall conclusion, therefore, is that Shipman killed about 250 patients between 1971 and 1998."