Despite this increase in complaints, compensation awarded by agents to consumers rose by only 1.4%, to a total of £2.2m.
The Property Ombudsman (TPO) has reported that it received 30,356 enquiries about dispute resolution services in 2019, up only 4% on 2018.
However, TPO's annual report found that of these, 5.106 went on to be formal complaints, a rise of 20%.
Despite this increase in complaints, compensation awarded by agents to consumers rose by only 1.4%, to a total of £2.2m.
TPO dealt with 2,518 complaints related to lettings, 1,669 relating to sales, and 780 relating to residential leasehold management in 2019.
The biggest awards in these categories were £17,664, £20,200 and £21,439, respectively, while the averages were £635, £742 and £273.
Management was the top cause of lettings complaints, while communication and record-keeping remained as the top cause of sales complaints.
The manner in which agents dealt with complaints was in the top three causes of complaints for lettings, sales and residential leasehold management.
In the minority of cases (0.1%) where agents were referred to TPO’s Compliance Committee for possible expulsion from the scheme for non-compliance, 98% paid the award to the complainant and only 22 agents were expelled from the scheme.
For lettings, 67% of complaints were supported by TPO, 50% were made by landlords, and 48% by tenants.
For sales, 63% of complaints were supported by the ombudsman, 67% were made by sellers, and 29% by buyers.
Katrine Sporle, property ombudsman, said: “2019 was another busy year for TPO.
"Complaints ascended year on year again and we also saw the complexities of cases increase, particularly in the residential leasehold management field.
"As always, I’m proud that the team rose to the challenge of rising complaint numbers.
"Our customer services team responded to a record number of people, over 30,000 initial enquiries raised, with nearly 10,000 of those received through our 24/7 online chat service, a 7% increase on 2018.
"Just over 25,000 enquiries that did not go on to become formal complaints saw TPO effectively assist consumers in other ways, whether that be signposting them to the correct place or person or giving advice and guidance to promote a local resolution between them and the agent.
"In order to further enhance consumer experience, TPO has translated its work in the initial enquiry stage into a self-diagnostic tool.
"Still in its piloting phase, we hope to promote the online tool this year.
"Overall, 2019 represented a year of growth and improvement.
"2020 has already brought a huge challenge with the outbreak of COVID-19.
"TPO acknowledges that the current situation is an extremely difficult one, for agents and consumers alike.
"TPO is here to help as best it can and is operating a full service.
"Consumers can still make a complaint at this time and the property industry can access information, guides and advice via our website.”
