'Most of these cases related to infringing clients' benefits like failing to confirm power of attorney or verifying whether the representative signing on behalf of the landlord or vendor was duly authorised,' said Steven Poon Kwok-lim, chairman of the estate agents' watchdog.

Last year, the watchdog received 669 complaints, compared with 746 in 2005 and 588 in 2004. However, the number of disciplinary hearings increased to 139 from 65 in 2005 and 108 in 2004.

Mr Poon said the figures showed an increase in the seriousness of complaints received, as more cases had needed to go to hearings.

By the end of last month, 128 cases had accumulated. 'We have to speed up as so many cases are pending,' he said, adding that the number of disciplinary committee members was recently increased from 18 to 23.

Last year, the spotlight fell on agents allegedly using their own cheques as initial deposits to show that there was interest in flats and collaborating with developers to trigger interest in the properties.

Mr Poon said that while these cases were serious, there had only been three such complaints.

The authority warned in November that the practice of agents using their own cheques might 'go against the principle of acting impartially and justly to all parties involved in a transaction'.

'We are consulting the ICAC [Independent Commission Against Corruption] on the formulation of practice directions regarding illegal kickbacks and unlawful transfers of clientele,' Mr Poon said.