Liberal Democrat health spokesman Norman Lamb has called for a formal investigation of independent sector treatment centres after HSJ revealed that the NHS paid for 50,000 operations last year that did not take place.

Mr Lamb said he would write to the National Audit Office calling on it to look into the matter. He is expected to send the letter this week. He said he is particularly concerned about guaranteed payments made under the first wave of ISTCs, which mean centres are paid regardless of how many patients they treat.

HSJ revealed that a number of ISTCs were seeing up to 50 per cent fewer patients than anticipated. This was 'immensely wasteful', said Mr Lamb.

'I have no problem with the diversity of supply but it is the central imposition of this and the guaranteed payments irrespective of the volumes of work they carry out which is highly questionable.'

Mr Lamb said his letter would request an investigation into whether guaranteed payment was an effective use of public funds.