Pharmacy leaders have hit out at the sector's paymaster after C+D revealed how NHS Prescription Services was calculating its accuracy by using the overpayments it makes every month to cancel out its underpayments (see Measuring accuracy).

The arrangement "whereby you can neatly massage your overall error rate by netting off the over and underpayments" was "preposterous", said Numark.

Given that the margin for error "now appears to be worse than the agreed level", contractors, particularly independents, would be "even more worried about whether they are being paid correctly", managing director John D'Arcy warned.

The comments came after C+D's Fight for Fairness campaign uncovered the paymaster's monthly error rates and calculations. The findings, which have been published on C+D's website in full, showed NHS Prescription Services had missed its 99.8 per cent accuracy target in 10 of the past 26 months.

Graham Phillips, a board member of the Independent Pharmacy Federation, agreed NHS Prescription Services' accuracy calculations gave no idea of the "swings and roundabouts" in payments for single pharmacies.

Mr Phillips also stressed that if the Department of Health wanted to demand quality from pharmacy contractors, it needed to deliver it itself, too. "The DH cannot have its cake and eat it – quality must be a two-way street," he said.

PSNC said in its annual report, which was published last week, that recent audits suggested that inaccuracy levels in prescription pricing were "declining". But it was "too early to be confident" in the improvements, the committee warned.

Fight for Fairness latest Who should be ashamed for poor accuracy? How accuracy is measured Accuracy checks reveal errors on almost 3 per cent of items