The Housing Ombudsman handed out more complaint handling failure orders (CHFOs) between January and March 2022 than any other previous quarter, according to a quarterly report.
The Ombudsman also recorded the highest number of non-compliance cases in a quarter seen to date, with 11 cases out of 32 CHFOs in which the landlords failed to comply within target timescales.
Lambeth Council was responsible for 4 of the 11 non-compliance cases and two cases involved Greenwich Council. Birmingham City Council and Lewisham Council also failed to comply in a case each.
Three out of four of Lambeth's CHFOs that the council failed to comply with were issued due to "unreasonable delays" in providing information to the Ombudsman.
The Ombudsman, Richard Blakeway, has been issuing quarterly reports on CHFOs since January 2021. In the same quarter last year (January and March 2022), the Ombudsman issued 10 CHFOs
Mr Blakeway said the number of orders issued this quarter and the high rate of non-compliance was "concerning".
He noted: "Across the first full year of issuing the orders, it is disappointing to see that some landlords appear in most reports, some several times.
"We recognise that landlords are under tremendous pressure, but these orders show the challenges that residents are facing trying to progress their complaints. This is eroding trust with residents.
"The leadership needs to focus on learning and redress, not on being defensive when things go wrong."
He added: "A positive complaint handling culture should promote learning and empower complaint handling teams to ensure they have the resources and respect to do their job. Landlords' governing bodies have a vital role to play in leading this culture which is why our Code sets out good practice for a member of the governing body to be identified as having lead responsibility for complaints.
"Now is the time to self-assess against the Code to ensure their organisation's approach is fit for purpose."
In March this year, the Ombudsman updated its Code, including a requirement for landlords to self-assess against the Code annually. The self-assessment is an important tool for landlords to assess whether their service is delivering a positive complaint handling culture for their residents, the Ombudsman said.
Landlords have until 1 October to become compliant with the strengthened Code.