Treatments available through the cancer drugs fund will have to continue being cut, the NHS England official in charge of the fund has said.

Peter Clarke, chair of the cancer drugs fund, said that given the growth in the cost of the fund, “there will be a need for further reprioritisation of what sits” in it in order to deal with its spiralling cost.

Under changes announced by NHS England earlier this week, eight drugs will cease to be available through the fund, while a further eight have had the range of conditions for which they can be prescribed reduced.

The fund has so far overspent its £280m budget for 2014-15 by £110m, Professor Clarke said at an event in London today.

Earlier this week NHS England announced a surprise £60m boost to the cancer drugs fund in the next financial year, bringing it up to £340m.

Professor Clarke acknowledged that the fund, which gives patients access to drugs considered too expensive to be commissioned by NHS England, had undermined the process created to appraise the cost effectiveness of drugs. The cost effectiveness is assessed by the National Institute for Health and Care Excellence.

Professor Clarke said: “The cancer drugs fund has had many consequences. One of them has been to undermine NICE and I regret that.”

He also admitted he had been against the fund’s creation in 2010, saying: “I’m involved in the cancer drugs fund because I want to sort it out. Did I agree with it being set up? No. I wanted to get involved in this is because before the fund was national [in 2013], the use of the fund in the south of the country was twice what it was in the north, because they had completely different policies. Now there’s a level playing field across different part of the country.”

Speaking at a seminar hosted by the Westminster Health Forum, Professor Clarke added that data that NHS England had hoped to gain on the outcomes of the drug treatments financed by the fund had not been collected “robustly” enough.

He said: “One of the things that we always wanted from the cancer drugs fund was this wonderful opportunity to get the real life outcomes of drugs that are largely used towards the end of people’s lives.

“Alas, the NHS has not been as robust in collecting these as we would have liked.

“However, with the establishment of the systemic anti-cancer dataset team in Oxford and the beefing up of our robustness of the financial penalties that will potentially come to NHS trusts [that fail to submit correct information] we are confident that data will be submitted in a much more coherent and complete fashion.”