Community groups have been left extremely disappointed after work on Hitchin Town Hall was approved retrospectively – with claims the council responsible has “marked its own homework”.

Restoration work carried out on the Grade-II listed building – previously described in the Comet as vandalism – was agreed by North Herts District Council’s planning committee last week after 13 of the 14 councillors voted in favour.

The plans were submitted by Buttress, the company appointed by NHDC as the project’s architects, after pipe work within the Brand Street building was installed in the ceiling of the foyer without the necessary approval from English Heritage – which deemed it to be a criminal offence.

Hitchin Town Hall Ltd was set up to help oversee the £4.39 million project to create a community facility and district museum serving Hitchin and Letchworth, but trustees have been critical of the council’s handling of the scheme.

The group’s chairman Stephen Pike said: “We are incredibly disappointed at the decision of the planning committee on the town hall. HTHL is concerned that NHDC did not choose to refer this late application to the secretary of state and did not seek external legal advice to confirm its interpretation of current law – independence in planning matters is extremely important. The danger is that NHDC could be challenged by taking this approach in choosing to ‘mark their own homework’.”

Mr Pike added that HTHL will be considering its position in light of recent events and the impact this decision may have on the project.

Mike Clarke, chairman of Hitchin Forum, said: “What the meeting could not address was the apparent sidelining of the town hall directors in the design process, which is incomprehensible.

“The way that the town hall appears to be suffering from a lack of due attention to a listed public building was partially corrected by the expressed concerns and action by the planning committee, for which we should thank them, and we hope that will be accepted and acted on by all those who are responsible for the completion of this important project.”

Robin Dartington, of Keep Hitchin Special, said: “It was disappointing that the detailed objections from community groups were ignored or evaded in the committee report. Only the opinion of the two officers mattered. But luckily at least some omissions of officers were picked up by councillors.”

A representative for Hitchin Historical Society also raised objections.

Councillor David Barnard, chairman of NHDC’s planning committee, said: “The committee is satisfied that the nature of the alterations being considered protect both the character and significance of the building and, with the conditions attached to the permission, are considered to be acceptable in listed building terms.”

Conditions were made to the colour scheme, relaid floorboards, pipe work and the entrance hall which would “preserve the special character of the listed building” according to council officers.