London social housing management body CityWest Homes has been placed under review, and its chief executive has stepped aside.
The Westminster City Council-led review comes after months of grappling with complaints about repair backlogs.
The arms-length management organisation (ALMO) provides services for more than 12,000 social housing tenants and 9,000 leaseholders on behalf of the council.
The move has brought renewed pressure from Labour opposition councillors for the council to bring its housing management inhouse.
Westminster's Cabinet Member for Housing and Customer Service, Andrew Smith, confirmed the review and chief executive Jonathan Cowie's resignation in a statement on Monday, June 25.
Cllr Smith said the review was aimed at enhancing the borough's residents' experiences and integrating housing services "more seamlessly."
"The scope of the review covers all areas from the shape and size of the arms-length management organisation, to how it delivers its core services to residents."
Cllr Smith said Mr Cowie "decided to leave CityWest Homes as he feels it is the right time to hand over the reins to someone new who can take the organisation forward in line with the council's new vision and mandate."
The statement was echoed by CityWest.
"We have been reorganising to improve services and reduce cost to residents," its spokesman said. "We know some services have not been as good as they can be, such as with our customer contact centre and repairs - where issues arose following the introduction of new contracts."
Westminster Labour leader Cllr Adam Hug said the review came after months of complaints by local residents and councillor campaigning.
He called the council's move a "belated recognition" of CityWest's problems, saying the Conservatives should take a share of the blame.
"It is clear the problem is not about individual members of staff - it runs much deeper."
Cllr Hug said Labour was calling for residents to have a greater say in housing management, arguing CityWest should be scrapped and social housing management responsibility brought back inhouse.
He said CityWest had struggled due to council decision-making, particularly over its call-centre service. He also labelled the council-commissioned 2015 Altair Review of CityWest's services "disastrous".
The review found CityWest was operating a good service, but judged it costly compared to similar models.
Earlier last year, CityWest set itself a goal of saving £5 million in operating costs over five years by reducing inefficiencies.
This March it told the council that after it streamlined its call centre operations and changed repair contractors mid-last year, customer contact handling and repairs performance dropped to "unacceptable levels."
One of its exiting contractors left a backlog of nearly 2,000 unfinished repairs.
It said the contractors changing, and heightened interest in fire safety following the Grenfell tragedy, also caused call volumes to increase.
This left its new repairs contractors unable to cope, it told the council.
CityWest said most repair calls were about drainage and plumbing.
It said performance had been "poor" from December to January. But by March, it had increased its workforce, and cleared the backlog.
"We have worked hard in rectifying this by increasing resources and reducing the backlog of repairs," CityWest's spokesman said.
"We now answer the majority of our calls within 30 seconds and in June we fixed 100% of emergency repairs and over 80% of routine repairs on time.
When asked in our post repair survey, 80% of residents who responded say they are satisfied with the service. However, it does not stop there and we continue to improve our services."
CityWest has been in operation in the borough since 2002, when it invested £200 million to improve the quality of housing in Westminster.
It manages housing estates including Lisson Green and Churchill Garden.
It carries out £14 million worth of repairs to the housing stock annually, and supports 27 resident associations and nine tenant management organisations.
Mr Crowie was chief executive for three years.
Cllr Smith said Sandra Skeete would be taking over in the interim.
"Jonathan has taken the organisation through an important period of transformation, and has shown commitment to delivering innovation in the way in which we serve the needs of our residents," he said.
"These have not been without their challenges, but Jonathan's professionalism and commitment to go the extra mile have been evident throughout."