In a review of nine health regulators, the Council for Healthcare Regulatory Excellence (CHRE) found the NMC closed cases ‘without adequate information,' and provides ‘generally weak or non-existent guidance' for the profession.
The audit analysed fitness to practice cases at the NMC between 2008 and 2009, when the CHRE's allegations of ‘racism and bullying' rocked the regulator and led to a series of senior resignations.
New processes are being introduced by the NMC that will raise standards, the audit concludes.
The GMC meanwhile was praised for resolving complex cases in a particularly thorough and timely manner.
A spokesman for the NMC said 'significant improvements' had been made since March 2009, including a reduction in the length and backlog of cases.
The spokeswoman continued: 'We are not complacent, however, and have a number of programmes in place to further improve our service in fitness to practise. We believe that future audits and performance reviews will demonstrate the progress we have made.'