The families of severely epileptic children have held a protest criticising the NHS for failing to prescribe medical cannabis.
The law changed in 2018, allowing doctors to legally prescribe cannabis for some serious conditions.
Although private doctors are issuing prescriptions costing up to £3,500 a month, families say they were promised the drug would be available on the NHS.
The government said it was working hard "to get these drugs available".
About 20 families travelled to Westminster to protest, calling for a judicial review of NHS rules and National Institute of Healthcare and Excellence (NICE) guidelines.
Two cannabis-based medicines, used to treat epilepsy and multiple sclerosis, were approved for use by the NHS in England in November.
However, Health Secretary Matt Hancock suggested issues surrounding the cost of the drugs were delaying the process.
Some families say they have resorted to paying up to £3,500 a month for private cannabis treatments.
They intend to seek legal advice in order to pressure the NHS to speed up the process.
Among them were parents, Ilmarie and Alex Braun, both aged 43 from Chester.
Their four-year-old son Eddie does not respond to typical medication but they say cannabis offers the most successful seizure control.
Mrs Braun said: "Today is renewed hope. Our children can not keep waiting, we can not keep fighting. It's exhausting."
They said they currently relied on money from charity to pay for a private prescription of £923 a month.
Dee Morris, 43, is spending £3,500 a month on treatment for Kayleigh Morris, 22, who can have up to 200 seizures a day.
She said it was "inhumane" to keep NHS patients waiting.
"My job is not campaigning. My job is not fundraising. This is what we have to do to get treatment for the ones we love.
"We're desperate. We've tried every other way."
Mr Hancock, who has met some of the families, said: "I changed the law to allow the cannabis-based drugs to be used in this country.
"There was then a report from the National Institute which decides what is paid for on the NHS.
"That report said that the costs that are being charged by the companies are too high.
"Since then I've been working incredibly hard to try to get these drugs available on the NHS."