A video in which Zac Goldsmith admitted being ‘bombarded with letters’ about Babar Ahmad between 2010 and 2012 has surfaced, despite his claim he had not heard of him until ‘quite recently’.

In response to Mr Goldsmith’s assertion Sadiq Khan’s support for Mr Ahmad was an ‘example of concern’, his mayoral rival pointed out he had also campaigned on Mr Ahmad’s behalf.

Mr Goldsmith countered by saying: “To say I campaigned on behalf of Babar Ahmad, who I had never heard of until quite recently, is an extraordinary thing to say.”

But in a video from 2012 Mr Goldsmith said: “Babar Ahmad is a story which has caught people’s imagination.

“I have been bombarded with letters from my local constituents – I’ve lost track of how many.

“I’ve had so many letters about him and others as well.”

Mr Ahmad, a British man of Pakistani descent from Tooting, was imprisoned in the UK without trial between 2004 and 2012.

He was subsequently convicted in the United States for ‘providing material support to terrorism’ in 2014, and sentenced to 12-and-a-half years in prison.

Mr Goldsmith also wrote a post on his own parliamentary website, ZacGoldsmith.com, detailing his meeting with MPs and human rights organisations to discuss a number of extradition cases including that of Mr Ahmad.

At the Conservative spring conference Home Secretary Theresa May highlighted Mr Khan’s relationship with Mr Ahmad, saying it was a ‘worry’ for a prospective mayor.

At the time Mr Khan said: “I’m amazed at the selective amnesia of Zac Goldsmith.

“Zac also campaigned to stop Babar Ahmad being extradited to the United States of America under the UK-US extradition treaty.”

Mr Ahmad said he received the ‘same level of support’ from Mr Goldsmith as he did from Mr Khan, and indeed Boris Johnson, in an interview with the BBC.

Mr Goldsmith was contacted for comment.