Medical cannabis confiscated from the mother of a child with severe epilepsy is to be returned after MPs and campaigners criticised the failure to provide adequate access to the potentially lifesaving medicine through the NHS.

Emma Appleby – whose daughter Teagan, 9, suffers from Lennox-Gastaut syndrome, which can cause up to 300 seizures a day – was “overjoyed” by the decision, but she renewed her criticism of the current system which she said “just isn’t working”.

The family had the medicine prescribed by a paediatric neurologist in the Netherlands but it was seized by Border Force officials on Saturday. They then obtained a private prescription from a specialist consultant in the UK before the health secretary, Matt Hancock, announced the £4,500 supply bought with crowdfunded money would be returned on Saturday.

“We’d fought for months to get access to medical cannabis in this country but were blocked at every turn, even though it’s now legal here,” Appleby, from Aylesham near Dover, said. “But overjoyed as I am, my heart goes out to those other families with severely epileptic children who are in the depths of despair.

“Neither I, nor they, should be put through this bureaucratic trauma. The system just isn’t working.”

The government was criticised by MPs on Monday after the confiscation of Appleby’s medicine highlighted the narrow guidelines governing access to cannabis medicines. Campaigners are unaware of a single new NHS prescription for cannabis oils containing significant amounts of THC since legalisation in November.

Despite the changes to the law, the medical community has been reluctant to allow prescriptions of medical cannabis, citing fears over the dangers of cannabis to the brain and calling for greater research. The British Paediatric Neurological Association and the Royal College of Physicians issued strict guidelines to clinicians, with the health service following suit.

According to NHS England, cannabis-based medicinal products should be prescribed only where there is “clear published evidence of benefit” and when patients have exhausted other treatment options. This has led patients to successfully seek access through private consultants, in what has been criticised as a system that favours the wealthy.

There are around 63,000 children with epilepsy in the UK and a third of those do not respond to the treatments traditionally provided by the NHS. Some 1,150 people died of epilepsy-related causes in 2009, according to the National Centre for Young People with Epilepsy.

Hancock tweeted on Friday night: “Happy to say that Teagan Appleby’s cannabis-based medicine has arrived and is ready to be collected. We are working hard across government to ensure we get these medicines to those who need them.”

He said last month he is working to “unblock” the system to allow greater access, but stressed “these things need to be clinician-led”.

Appleby urged Hancock to “follow through on his recent supportive words and unblock the system … Those with the power to sort this need to, and fast.”