A flagship fund to pay for cancer drugs in England "has not been managed effectively", a Westminster spending watchdog has found.
The House of Commons Public Accounts Committee (PAC) found that NHS England overspent the Cancer Drugs Fund's £480 million budget by £167 million over the course of two years, but did not take action to control costs until the end of this period.
While 80,000 people received drugs through the Fund, it was "unacceptable" that the Department of Health and NHS England did not have the data needed to assess whether patients' lives had been extended or whether the spending was a good use of taxpayers' money, said the committee.
Launched in 2010, the Cancer Drugs Fund has been repeatedly cited by Prime Minister David Cameron as an example of his Government improving services for NHS patients. At Prime Minister's Questions in the House of Commons on Wednesday, he described it as a "key difference" between the health services in England and Wales.
But the PAC found that there was agreement that the Fund was "not sustainable in its current form". NHS England and the National Institute for Health and Care Excellence (Nice) are in the process of consulting on proposals to reform it from April.
The report questioned whether the Department and NHS England were using their purchasing power effectively to obtain a fair price for cancer drugs, and it called for them to make clear whether people in different parts of the country were getting equal access to the Fund.
The report found that the Fund's budget was overspent by a total of £167 million in the years 2013/14 and 2014/15. And it noted that the annual cost of the Fund grew by 138% from £175 million in 2012/13 to £416 million in 2014/15. But it was not until November 2014 that NHS England started taking action to control costs, the committee said.
Committee chair Meg Hillier said: "The Cancer Drugs Fund has enabled thousands of people to receive drugs not normally available to them through the NHS. While this is welcome, it's also clear the Fund requires significant and urgent reform if it is to be sustainable.
"A vital step in addressing the financial challenges must be to properly evaluate the health benefits of drugs provided through the Fund.
"If cancer patients seeking its support are to get the best possible treatment then there must be confidence that public money is being spent on the right medication, and at a fair price.
"We will be closely monitoring the progress made by the Department and NHS England in the months ahead."
An NHS England spokesman said: "This report comes just a day after new independent figures showing the NHS's great success in improving cancer care and survival rates for patients across England.
"While we welcome the Committee's support for a redesigned Cancer Drugs Fund, we hope their explicit call for cuts to cancer drugs prices charged to the CDF will be borne in mind as complex decisions on its future are taken in the next few months."