Women with advanced breast cancer in Wales are to be deprived of a drug that could give them at least six months longer to live, because the high price makes it unaffordable for the NHS.

The National Institute for Health and Care Excellence (Nice) says in its final guidance to the NHS that Kadcyla is too expensive. The decision in effect sets up a postcode lottery in the UK because a special government fund will continue footing the bill for women who need it in England.

It means women in Wales will be unable to obtain Kadcyla on the NHS, while some women in England will have the cost paid by the government’s Cancer Drugs Fund. Scotland has a separate process, but the drug is not available there either.

Kadycla can give women with a particular kind of advanced breast cancer an extra six months of good-quality life – and sometimes longer. But the manufacturer, Roche, pitched the full list-price of treatment at £90,000 a year, said Nice. That is three times the acceptable price for cost-effective medicines and nearly twice the ceiling for drugs at the end of life.

Roche has since done a deal with the Cancer Drugs Fund, set up by the government to pay for drugs that the NHS in England ordinarily could not afford. The amount of the discount is commercially confidential.

But this substantial discount has not been extended to Nice, which has now published its final guidance on the drug. Roche offered a deal, but it was not enough to bring the price within the Nice upper threshold of £50,000.

Sir Andrew Dillon, the chief executive of Nice, said: “We recognise that Kadcyla has a place in treating some patients with advanced breast cancer and we have been as flexible as we can in making our recommendation. However, the price that the manufacturer is asking the NHS to pay in the long-term is too high.”

Breast Cancer Now, which has been lobbying Roche to reduce the price, called on David Cameron – who set up the Cancer Drugs Fund – to intervene. “This is hugely disappointing news, particularly for anyone who could benefit from Kadcyla in Wales, as they are also not covered by the Cancer Drugs Fund,” said Dr Caitlin Barrand, an assistant director.

“We simply cannot continue in this way, with highly effective new cancer drugs being held just out of reach for patients in certain areas of the UK. This drug isn’t available to those that need it in Scotland either, and had Roche failed to collaborate with NHS England in the last round of delisting from the fund, patients in England might be missing out too.

“It’s time that the prime minister showed real leadership on this issue. People living with incurable cancer don’t have time to lose, and a fairer, more flexible system that enables access to the best treatments available on a routine, UK-wide basis is long overdue.”

The Cancer Drug Fund was a response to the anger of cancer patients and their families, reflected in front-page tabloid headlines, whenever Nice turned down a drug that might benefit people who were terminally ill on the grounds that it was not sufficiently cost-effective. Roche, which makes a number of cutting-edge cancer drugs, has been a major recipient of the fund.

The fund has become unaffordable. It was established in 2010 at £200m a year but its cost is projected to rise to £410m this year, according to NHS England, which now runs it. Kadcyla was one of a number of drugs that were threatened with de-listing earlier in the year, but it was reprieved after Roche agreed to discount the price charged to the fund.

The fund is due to end in April 2016, at which point drugs such as Kadcyla will not be available anywhere on the NHS unless a new mechanism is put in place.