Spiralling temperatures within a "poorly ventilated" block of flats in Wakefield reached well above 40C this summer, it has emerged.
Wakefield Council said it had received a complaint from a resident about the block, which was backed up by findings from officers sent to inspect the building.
They found the temperature within the flats, which were built out of a converted office block, was 15C higher than that outside.
The council was asked whereabouts the property concerned was, but it said it would be "inappropriate" to reveal its identity, citing an "ongoing investigation" into the matter.
But in a report, deputy leader Denise Jeffery suggested that a lack of planning regulations for converted properties, which limits councils' involvement in the process, meant that the issue may have been overlooked.
She said: "The housing standards team has recently received a complaint from a resident living in a new block of flats in Wakefield which alleges that the flat is poorly ventilated and too hot as a result.
"On the day of the visit, the outside temperature was 22C and the inside 37C. During the few very hot days we had recently, temperatures were apparently into the mid-forties.
"Complaints of this type are unusual as newly built or converted properties are subject to controls in the planning process which are supported by input from
"In this instance, however, the flat is within a block recently converted from a former office building. This type of development can be undertaken using permitted development rights which remove much of the council’s ability to influence the changes being made."
Coun Jeffery added that the local authority would "engage with the landlord" in a bid to make improvements for tenants.
Her report will go before a full council meeting on Wednesday.
Local Democracy Reporting Service