Persimmon Homes sought outline permission for up to 144 homes on the 5.6 hectare former Wardley Colliery site, which is in the green belt in the Wardley area of Gateshead.
The application was approved by Gatehead Council members at a planning committee meeting on Wednesday, against officers' advice.
According to a committee report, the larger eastern portion of the site contains the former JW Coats and Sons Ltd yard, which is currently vacant save for one warehouse building. Meanwhile, the smaller western portion of the site "contains the dangerous ruined remains of several buildings associated with the historic operation of the colliery".
The report went on to say that the applicaton was backed by 140 letters of support, all individually signed by local residents, and delivered to the local authority in one bundle in April this year.
However, the report said suspicions were raised when Gateshead officers noticed one of the letters appeared to have been written and signed by the spouse of a member of the council’s planning team.
"Upon contacting this person, they confirmed that they had not written any letter and had not signed any document in support of this application," officers wrote in the report.
When the council asked signatories of the letters to confirm their authenticity they received 21 responses from residents who advised they hadn’t sent the original letter, "some saying they had never heard of Wardley Colliery or what the application proposes," officers wrote.
"Overall, 48% of the people who responded and 15% of the total number of letters received are known to be false representations, which officers consider reduces the weight that can be given to the rest of the bundle of letters, which should be treated with some caution in terms of being a true reflection of the level of support for this application," said the committee report.
In addition, officers said the landowners, "in agreement with the applicant", hand delivered flyers and questionnaires to neighbouring homes asking residents to support their application.
The report states: "Having seen the content of material distributed, officers have serious concerns due to the factual errors contained, especially in relation to stating that Mr Coats’ yard will open as a waste transfer station (WTS) if permission is not granted.
"Mr Coats’ yard does not have permission to operate as a WTS and would need a change of use to operate lawfully and would be open to Enforcement action without it.
"The LPA considers that the these documents are misleading as they do not factually represent the application and could be perceived by a recipient as exaggerated and intimidating, as well as showing imagery that is not a true representation of the application site."
In response to Planning, landowner Bill Coats declined to comment. But Colin Ford, who co-owns the smaller section of the colliery land, said: "I don't know where the letters came from to be honest with you. I have no idea."
However, he said he was responsible for sending out the leaflets that the council described as misleading and accepted there may have been minor mistakes, adding: "It wasn't intentional."
A spokeswoman for Persimmon Homes said: "As a developer we are confident that we have submitted a fair and accurate report to support the application for much needed housing and await Gateshead Council’s decision."
A decision on the planning application was twice deferred by councillors after officers recommended refusal.
The committee report describes the proposed scheme as "inappropriate development in the green belt" and says it would have a "detrimental impact" on local wildlife that "could not be appropriately mitigated against". But members of the planning committee approved the scheme at Wednesday's meeting.
Major housing schemes to have been approved in Gateshead this year include plans for 582 homes on a former green belt site.
In November, Durham County Council approved plans for a 1500-home scheme near Seaham, despite the site’s allocation for employment use.
And in April, Darlington councillors gave the go-ahead for 800 homes on unallocated sites, despite the council having identified a six-year housing land supply.