A bid for permission to put a large two-bedroom mobile home in the back garden of a property in a conservation area has been successful.

The application from Michael Boyle, of Lower Green Road, Pembury, upset many of his neighbours who said that although the building was being described as a mobile home, it was effectively a new dwelling in the rear of the Grade II listed property.

However, Mr Boyle told Tunbridge Wells council that the structure, which would rest on plinths on the ground, could be moved and therefore could correctly be classed as a mobile home.

The council agreed and has issued him with a Lawful Development Certificate.

The decision has been heavily criticised.

Brian Hemsley, of Lower Green Road, who lives next door, said: "If this application had been for a two-bedroom bungalow within the curtilage of this listed building, in a conservation area, it would have required full planning permission which would have been rejected."

Mr Hemsley said that Mr Boyle's use of the 1968 Caravan Act had enabled him to gain permission for a home that was significantly larger than a two-bedroom bungalow.

Several neighbours attended the last planning committee of the parish council to protest and – by chance – Carlos Hone, the head of Tunbridge Wells Borough Council's planning department, was present.

Sarah-Jane Falkner said: "Short of calling for a judicial review, it seems there is nothing we can do now."

Mr Hemsley said residents would still be pressing for an explanation of how the decision – including a decision to allow Mr Boyle to fell seven trees in his garden – had been reached.

Mr Hemsley said: "Someone needs to be accountable for this."

Pembury Parish Council said: "We were very disappointed that a lawful development certificate was granted given residents' concerns. We have not considered any further action as we do not believe that any further action is available to the parish council once the certificate has been issued."

The council said: "Mr Hone was at our meeting, but he had been invited some time ago in order to update the committee about other matters.

"However, it was useful to have him there to explain the rationale of the decision on the lawful development certificate."

Mr Boyle has said that the mobile home would be used by his mother as an annexe to the main house.

It will not have a separate address, post box, utility meter, parking, garden nor a separate access and the entire structure remains temporary and could be lifted out by crane.