Syed Hussain, 52, has been locked in a legal battle with Hillingdon Council since 2010, when a demolition notice was served against the addition to his home in Pole Hill Road, Hillingdon.

The council says the extension was originally a one-storey garage but a second storey was added later, bringing it above the height given planning permission.

A planning inspector has already dismissed Mr Hussain’s appeal against the enforcement notice.

Two subsequent applications to the High Court to judicially review the appeal decision were also refused, at a cost to Mr Hussain.

Jean Palmer, deputy chief executive and corporate director of residents services, said: “Officers visited the site on Monday to remeasure the height of the outbuilding, which is more than 5.5 metres high, the measurement as considered by the courts.

“This two-storey outbuilding does not benefit from planning approval, as it is significantly different from the plans that were approved in 1996.”

Ms Palmer added: “The size and scale of the building results in an over-dominant and visually obtrusive form of development. It is considered to be to the detriment of the character and appearance of area, and has the potential to become a lived-in property, which is not acceptable.

“We have had ongoing conversations with the owner to advise on the steps he must take and if he continues to ignore this we will take enforcement action.”

Mr Hussain, who lives with his partner and two children, insists the building is not too tall.

“The council have not measured it from the outside when I have been there,” he said. “It has not changed in height since it was first built in 1994.”

Mr Hussain received part-retrospective planning permission for the structure in 1996.

“The only change was the addition of a dormer in 2008,” he claimed. “That was approved by the council and does not make the roof any higher.”

He said the building is not more than five metres high. He believes the council may have taken the measurement from a section of land outside the extension which had been dug up and lowered, meaning the measurement appeared higher.

“They’re trying to make an example out of me,” he added.

Mr Hussain has been told that if he does not make the required changes soon, the extension will have to be torn down.