Complaints about estate and lettings agents jumped by 23% in 2013 compared to the previous year.
The Property Ombudsman (TPO) – which runs a voluntary redress scheme – received 16,000 enquiries to do with disputes in 2013, of which 60% concerned problems with letting agents.
While the number of complaints enquiries to do with letting agents rose by 22% to 10,179 compared to 8,334 in 2012, the 2013 figure had doubled since 2009 (5,551).
In 2013, the enquiries that resulted in a formal review by TPO were mostly to do with a breakdown in communication between the agent and the landlord or tenant (13%).
Poor complaints handling accounted for 11%, while trouble with deposits (8%), repair and maintenance (8%) and check in/out and inventories (7%) followed closely behind.
Enquiries relating to letting agents that had not signed up to the voluntary code of conduct and redress scheme overseen by the TPO increased by 34.2% between 2012 and 2013.
Ombudsman Christopher Hamer said he expects even more complaints about lettings agents in 2014.
He said: "2013 was a significant year for many reasons, with industry consultations, legislation changes and regulatory reforms, including the Enterprise and Regulatory Reform Act receiving Royal Assent, which will make it a legal requirement for all letting agents to register with a redress scheme."
"With 10,000 letting agents already voluntarily registered with TPO by the end of 2013, 60% of the cases I reviewed resulted from landlord and tenant complaints, and I expect we will see even more in 2014 in light of the changes."
While the Act makes some progress in protecting landlords and tenants from rogue letting agents in England – and will make them all sign up to one of three redress schemes later this year – it stops short of fully regulating the sector. TPO is calling for further legislation and a consistent approach across the UK.
Meanwhile, complaint enquiries to do with estate agents were up 25% year-on-year in 2013. Poor communication, failures in the duty of care and fees accounted for the lion's share of complaints.