Tenants and landlords accounted for over 85% of complaints made to The Property Redress Scheme (The PRS) in 2016.
The organisation's annual report reveals that the most common cause for complaint was property management, accounting for 29% of all complaints.
This was followed by 'deposits' (27%) and 'problems with rent' (15%).
Some 51% of complaints made to the scheme were from tenants, while landlords were responsible for 35%. Property sellers and buyers, meanwhile, were responsible for just 4% combined.
According to the report, the scheme received 40% more formal complaint notifications in 2016 when compared with the previous year.
“Although formal complaints have risen, so too has the number of complaints resolved at the early stages of our process," says Sean Hooker, The PRS' head of redress.
"Around 40% of our cases are resolved at recommendation stage and 99% are dealt with in less than 90 days from receiving the initial complaint through to a decision."
The PRS - one of three government-approved redress schemes - also reports that its membership increased by a third last year.
At the end of 2016, the organisation boasted a membership of 5,529 agent offices (31% sales, 79% lettings), alongside 227 other property professionals such as independent inventory clerks.
Hooker says the rise in complaints, while partly down to the redress scheme's significant growth, can also be attributed to higher consumer awareness of the complaints process.