Neighbours fear the “historical aspect” of an eighteenth century listed building may be lost if it is revamped into 92 new homes and a supermarket.

Applicant St William Homes is proposing to restore the site of the former gas holder site and Grade II* listed building Frogmore House, in Lower High Street, Watford, into new homes and a Lidl store.

A decision about the proposals will be made at a Watford Borough Council Development Management Committee meeting on Wednesday, November 29.

The first single storey rear extension of Frogmore House could also be refurbished into office space.

Antoinette Batten, who lives in a Frogmore Cottage, in Lower High Street, feels the building should be “protected”.

She said: “Overall, I support the restoration of Frogmore House, but as an ex-resident of the property I have some concerns that part of the historical aspects of the building may be lost.

“I am particularly concerned at the loss of the single story extension that St. Williams plan to demolish. Although this "extension" may only date back to the 1800's, I feel it still has some historical interest.

“It contained access to the basement where the original water well was, and it was only accessed by the back stairs which went from the scullery to the servants quarters at the top of the house. Because of this, I feel it is an integral part of the buildings history and should be protected by the buildings Grade II* listing.”

Richard Searle, of Lower High Street, added that he was concerned new homes could increase traffic levels.

He said: “I have owned my property for 28 years, therefore making me very aware of the area's traffic problems etc. Firstly I feel that the proposed same entrance and exit for the development is particularly ill-considered with regard to emergency services trying to access Thomas Sawyer Way to Watford Hospital as Lower High Street already has queues of traffic at peak times coming from Waterfields Way.

“If granted not only will this cause further disruptions to the drivers who use this route to work but could result in a serious delay for the ambulance or police service. Also a problem that frequently occurs as a result of the two lanes converging on to Lower High Street from Waterfields Way is that drivers need to filter in to one lane before the traffic lights by Seat.”

Suzannah Fleming, Chairman of The Temple Trust, a historic building preservation trust, said: “Key details are lacking for the proposed re-instatement of various features such as the front door case, the garden door case, the hopper heads and downpipes.

“If there was a commitment to a conservation programme being led by a conservation architect then it would be of less concern than it is at present.”

A Watford Borough Council spokesman said that if the plans go ahead, there will be a commuted payment of £750,000 towards the provision of affordable housing in Watford, along with a community infrastructure Levy payment of £1.85M towards new infrastructure and a re-profiling of River Colne embankment to reduce flood risk.

They said: “Our officers have assessed these plans and recommended that the Development Management Committee approve them for planning permission – subject to a series of conditions.

“However, the final decision will be up to councillors on the Development Management Committee.”

A spokesperson for St William Homes added: "We have worked closely with the local community on the development of the proposals for the Watford Gasworks site and responded to feedback in our final plans. From the creation of more homes for Watford to the provision of a discount food store, we have listened carefully to what local people want and need.

"The future of Frogmore House was also highlighted as a local priority. The plans will deliver an extensive restoration of the building, which has fallen into disrepair, and bring it back into active use after many decades.

“The proposed scheme is carefully designed to fulfil the potential of this complex brownfield site for the benefit of both new and existing residents.”