A pensioner lay dead in his home for six years before his skeletal remains were found - after his landlord obtained a court order to enter and check the gas supply.
The body of Robert Alton, who was 76, was discovered inside his flat in Bolton, Greater Manchester, on March 9 this year.
An inquest into his death concluded he 'likely' died in May, 2017, said his landlord Bolton at Home in a statement after a coroner recorded an open verdict.
The housing association owns, manages and maintains more than 18,000 homes across the town, reports the Manchester Evening News.
Its chief executive officer said in a statement after the inquest 'it's completely unacceptable to us that something like this has happened' - and admitted the organisation should have done more to check on Mr Alton's welfare.
In the statement, CEO Noel Sharpe said Bolton at Home 'made many attempts' to contact him 'over a number of years' to arrange gas safety checks, but the inquest heard there was no response from him.
It's understood the pensioner's rent was being paid through housing benefits. His death was not treated by Greater Manchester Police as suspicious.
Mr Sharpe said the 'reason' Mr Alton's death wasn't discovered sooner was 'our previous procedure, while meeting legal requirements, wasn't strong enough to prevent something like this happening'.
He said the policy was changed in July 2022 so legal warrants would always be sought to obtain access to tenants' homes where they cannot be contacted to check gas supplies. It was that change that led to Mr Alton's body being discovered, the inquest heard.
In the statement, Mr Sharpe said Bolton at Home missed opportunities in spotting something was wrong and 'didn't go far enough' to investigate why he couldn't be contacted.
He said: "On 9 March 2023 we learned of the death of our tenant Robert Alton after his body was discovered at his home in Hemsworth Road, Bolton. The subsequent police and coroner's investigation has concluded Robert’s death was not suspicious and that he likely died in May 2017
."Everyone at Bolton at Home has been deeply shocked by this and we realise it will concern and upset people to learn his body remained undiscovered for such a long time. It’s completely unacceptable to us that something like this has happened, and we've taken action to reduce the risk of it happening again.
"The reason we didn't discover Robert's death for so long is because our previous procedure, while meeting legal requirements, wasn't strong enough to prevent something like this happening.
"We made many attempts to contact Robert over a number of years to arrange gas safety checks. It's clear that the action taken by us to understand why we couldn't contact him didn’t go far enough. Opportunities were missed in spotting that something was potentially wrong. We should have done more to check on Robert's welfare.
"We changed our procedure in July 2022, and we now immediately begin the process of seeking access to someone's home via a warrant in instances where we cannot contact them to arrange a gas safety check. It was this change and subsequent review of previous instances that ultimately led to us seeking a warrant to access Robert's home and discovering his body.
"The change to our procedure significantly reduces the risk of something like this from happening again. In addition, we’re also taking steps to enable our tenancy support team to work more closely with our gas safety team where we’re struggling to gain access to a property and where there may be welfare concerns.
"We're also exploring what else we might be able to do to further reduce the risk of this being repeated.
"I would like to offer our heartfelt condolences to Robert's loved ones, friends and neighbours and apologise to them for the opportunities we missed in finding out why we couldn’t contact him."
Coroner Peter Sigee recorded an open verdict. No relatives have been traced, despite GMP issuing an appeal for any to come forward after his death.
