Scores of people with multiple sclerosis (MS) have suffered debilitating side-effects after being put on to a cheaper new drug as part of an NHS drive to save money.

About 170 MS patients at Charing Cross hospital in London have had complications, including a relapse of their illness, after being switched from Tysabri to a different drug called Tyruko, made by the pharmaceutical company Sandoz.

In a handful of cases, the people affected developed such serious symptoms that they had to be taken to hospital for treatment. Patients have told doctors about side-effects including an inability to use their legs, other mobility problems, fatigue, pain and sudden weight gain.