Medicinal cannabis should not be treated differently to other drugs and its effects must be thoroughly investigated, MPs have been told.

Professor Chris Whitty, chief scientific adviser at the Department of Health and Social Care (DHSC), warned that rushing the development of medicines risked creating a “disaster” like the thalidomide scandal.

Giving evidence to the Health and Social Care Committee, he called for a responsible approach to medicinal cannabis, based on evidence.

Medicinal cannabis was rescheduled by the Government last year, allowing doctors to legally prescribe products and clinical trials to take place.

However, campaigners have complained that they are being denied NHS prescriptions because professional guidance on when it should be used is too restrictive.

The committee heard that while medicinal cannabis has been rescheduled, there is a lack of scientific research proving products are safe and effective and they have not been licensed.

“It’s very dangerous to have a cannabis exceptionalism here,” Prof Whitty said.

“These are drugs, they have side effects, they have positive effects – that is clear.

“What we have to do is balance those two, but they are no different to any other drug in that sense.

“And if you look at the history of medical development, history is littered with people rushing things through and ending up regretting it or, in a few cases – thalidomide probably the most well-known – having an absolute disaster on their hands.

“So it is really important that we balance throughout this a responsible look at the side effects of the drugs and the positive effects of the drugs.”

Professor Finbar O’Callaghan, president of the British Paediatric Neurology Association, told the committee he was “completely behind” the decision to reschedule medicinal cannabis products.

But he warned that some people had interpreted this to mean they “are now freely available in the NHS for doctors to prescribe”.

“It’s the doctors who then look at this and see that the evidence base in that particular area isn’t there, therefore are reluctant to prescribe them,” he said.

Prof O’Callaghan said it could take three years for randomised controlled trials to be completed.

“I think we need to get the evidence and I really think there’s a question here about whether these medicines will help children and we need to answer it,” he added.