The Nursing and Midwifery Council (NMC) is becoming more proactive in its approach to investigating complaints.
This year the NMC fitness to practice team carried out 2287 preliminary investigations compared with1830 in 2006.
Annual accounts show that fitness to practice analyses were the NMC's largest area of expenditure, at £10m.
This was followed by £5.7m costs of maintaining the register and £3.3m costs of promoting and developing standards.
The organisation says it takes a "risk-based approach" to the allocation of funds for priority areas such as fitness to practice.