Zac Goldsmith repeatedly lobbied ministers on behalf of those campaigning to prevent Babar Ahmad's extradition, despite claiming to have only heard of him "quite recently," Politics.co.uk can reveal.
Ahmad, who has since been convicted in the US for "providing material support to terrorism," was one of several controversial figures which the Conservative party have accused Labour's Sadiq Khan of "giving cover to" in the past.
Home Secretary Theresa May singled out Khan's prior association with Ahmad at a joint appearance with Goldsmith earlier this month, saying it was a "worry" for somebody campaigning to be mayor.
Speaking at a debate earlier this month, Goldsmith added that Khan's support for the campaign against Ahmad's extradition was an "example of concern" and said that Khan had "campaigned very actively for him."
When Khan replied that Goldsmith had also campaigned on Ahmad's behalf, Goldsmith vehemently denied it 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."
However Politics.co.uk subsequently uncovered video showing Goldsmith speaking about Ahmad's case back in 2012. He told an anti-extradition meeting that "Babar Ahmad is a story that has caught people's imagination" adding that he had been "bombarded with letters" about his case.
In fact I can now reveal that Goldsmith himself also penned letters on behalf of the campaign for Ahmad.
Correspondence seen by Politics.co.uk reveals that Goldsmith wrote to two government ministers between 2010 and 2012 about Ahmad's case.
In an email from 2012, Goldsmith tells one of his constituents that he "shares your concerns about [Ahmad's extradition]."
He adds: "It seems bizarre that we cannot get rid of people like Abu Qatada, but cannot protect others. I have raised the issue of our extradition arrangement with the US, in Parliament, and in letters with Ministers and will continue to pursue this."
In later correspondence, he reveals that he has "raised the issue of our unsatisfactory extradition arrangements with the US on many occasions, and will continue to pursue this particular case."
Further correspondence obtained by Politics.co.uk reveals that Goldsmith lobbied ministers about Ahmad's case six years ago. In 2010 he wrote to then counter-terrorism minister Baroness Neville-Jones about the campaign to prevent Ahmad's extradition to the US.
Neville-Jones replied that it would be "wholly inappropriate" to delay Ahmad's extradition.
"Failure to comply [with the extradition request] would not only place the UK in breach of these obligations but would also jeopardise the UK's ability to seek the extradition of persons from other countries," she added.
Seventeen months later Goldsmith wrote to then immigration minister Damian Green about the case. Green replied that the US was "entitled to seek his extradition."
One constituent, who contacted Goldsmith about Ahmad's case, told Politics.co.uk that he was surprised to hear Goldsmith deny knowledge of Ahmad, given his longstanding involvement in the campaign.
The constituent, who does not wish to be named, said that Goldsmith had been a regular visitor to his local mosque in Kingston, where he had built up good relations with people from the local Muslim community, both on this issue and others.
However, he added that those relations were now seriously damaged due to the manner in which Goldsmith had fought his campaign against Khan.
"I was pro-Zac and anti-Sadiq," he told me.
"Zac has been a good friend to the community. He's come to our mosque several times. The times I've met with him he seemed like a genuinely nice bloke and I thought I could trust him. I spoke to him about housing and he impressed me.
"I was planning to vote for him and I even had raging debates with some of my friends in his defence. He seemed like a known quantity compared to Sadiq and I was ready to back him but how his campaign has gone in recent weeks seems completely out of character. I think the people behind him have taken control."
Asked about Goldsmith's 'extremist links' allegations against Khan, he replied: "I think he's trying to ride the current tide of anti-Muslim feeling. It's very trashy and below the belt. I'm more concerned about issues like schools and housing. We can't afford to get property now and I wish he would focus on that."
Asked whether Goldsmith's campaign would damage relations with the local Muslim community, he replied: "It will strain relations. Me and my friends are very disappointed, saddened and angry that he has decided to take this path."
A new poll out yesterday suggests that Goldsmith's extremist allegations against Khan have yet to break through with Londoners. The YouGov poll for the Evening Standard found that Khan has extended his lead to 16% over Goldsmith on first preferences. Khan also had a lead on which candidate "will tackle Islamic extremism" while Goldsmith had a lead on which candidate is more "divisive".