Medical cannabis will be available on prescription in the UK within a month, The Telegraph can reveal.

The Home Office will announce the “rescheduling” of cannabis-derived medicines in Parliament, lifting restrictions which mean that until now it has only been allowed in the most exceptional circumstances.

Under the new rules, those suffering chronic pain, severe epilepsy or nausea as a result of chemotherapy could be prescribed the drug by specialist doctors, this newspaper understands.

An announcement is expected in Parliament within a fortnight - allowing the drug to be legally prescribed within a matter of weeks.

The changes, which follow a long battle by campaigners, mean Britain will be among the most liberal in Europe when it comes to medical cannabis, joining countries such as Germany which gave it the green light last year.

There are an estimated 28 million people living with chronic pain in the UK, including those suffering from conditions such as arthritis and multiple sclerosis (MS).

The MS Society estimates that 10,000 people suffering from that condition alone could benefit from the treatment.

But it is not known how many cases will be granted access to the drugs.