The Al Jazeera news website has dubbed Williamson’s fire apparatus, a $1bn (£700m) multi-purpose apparatus which was installed in his office, as a “village fire brigade”.
The apparatus is said to have been installed in December 2015 by the British fire service, but its true origin is not known.
The fire brigade’s chief inspector, Nick Taggart, told Al Jazeera the fire brigade had “no idea” why the apparatus was placed in the office of the former Prime Minister.
Taggart said the fire service had been told by an unnamed “senior fire official” that “it was the work of the fire department and we were told by them to put it there”.
The fire service has also denied the claim.
The apparatus was installed on the premises of Williamson, a former Conservative politician who was also the Conservative leader at the time of the Grenfell Tower fire.
Williamson had left his post as Tory leader after the election of Donald Trump.
He subsequently quit politics, but returned as leader of the Conservative party in September 2017.