The Ombudsman for Estate Agents (OEA) received more than 8,000 complaints from unhappy clients last year - up by more than a third on 2005.
Bungled administration, fees and sales details, such as room measurements, were the main sources of contention.
The ombudsman warned that agents would suffer as private sales websites grow.
But the National Association of Estate Agents said the rise in complaints could reflect the increasing numbers of agents signed up to the scheme.
Specific details of what riled home buyers and sellers in 2006 will be released on 23 May in the industry body's annual report.
Inherent stress
The OEA offers an independent service for dealing with disputes between members of the scheme and consumers who are actual or potential buyers or sellers of residential property in the UK.
According to Chris Hamer, head of the service, the rise in the number of complaints was "down to people being less ready to be satisfied with something which they perceived as poor service - given the size of the financial commitment that they're taking on".
"It just means more people are being pulled in line"
The "inherent stress" in the process of buying and selling houses means if something goes wrong estate agents are an "easy target" for people to blame, according to Mr Hamer.
A recent survey suggested that fees paid to estate agents had almost tripled over the past decade, as house prices soared but charges barely changed on a percentage basis.
Peter Bolton King, chief executive of the National Association of Estate Agents, insisted the surge in complaints was "not necessarily negative".
He argued it could be attributed to the growing number of agencies belonging to the ombudsman scheme since it was set up in 1998 and the public's growing awareness of its existence.
"It just means more people are being pulled in line," he said.
But the boss of a private sale website predicted a fifth of estate agents will be forced to close in the near future if they don't improve their service.
"They have to stop lying to customers," said Martin Charlick, managing director of The Little House Company.
"They have to stop using completely unfair and unjustified contract terms, and they have to actually provide a service that is worth what they expect to charge."
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