Zac Goldsmith will appear on Channel 4 tonight to defend the election expenses currently under investigation by the Electoral Commission.

Channel 4 News and the Bureau of Investigative Journalism have accused the Richmond Park and north Kingston MP of not declaring the full cost of materials used in his campaign.

The channel ran an exclusive report on Thursday night, in which Jon Snow said Mr Goldsmith was welcome on the programme to have a live interview, but had spoken to Sky News instead.

Mr Goldsmith said: "It ended with Jon Snow saying that I'd spoken to the BBC and Sky, and that he'd be 'delighted' to have me on to reply. The clear implication was that I'd chosen not to.

"In fact, Jon Snow knows very well that I did try to respond to Channel 4 directly. I offered to address the points they raised in a live interview after the report, but they refused point blank.

"Instead, they asked for a written statement. They even added that without one, they would end the report with the words 'Zac Goldsmith declined to comment'.

"So I did submit a comment. It went: 'I offered at 5.30 today to do a live interview addressing the issues raised in this item but was told by Channel Four that this was not possible”. Not surprisingly, they didn’t use my statement."

This sparked a Twitter exchange between Mr Goldsmith's sister Jemima Khan and Jon Snow, with Miss Khan tweeting at the news presenter: "Why didn't Channel 4 allow Zac on tonight to respond live to your programme as he requested?"

Mr Snow responded: "He decided to go to Sky instead. We had been asking him for a response for a number of days but until today he refused to comment."

Mr Goldsmith also claimed in an interview with Sky News that he was targeted because he was a high profile figure and accused Channel 4 However, a Channel 4 spokesman said: "We refute any suggestion that Zac Goldsmith was targeted simply because he is a high profile figure.

"The questions we have raised relating to his expenses are entirely legitimate. The issues we found regarding Mr Goldsmith's campaign expenses are materially different and of a different scale to those found in other returns we looked at.

"We informed Mr Goldsmith of our report last week and he was given ample opportunity to respond on the record to these questions.

"Channel 4 News stands fully behind its report which was rigorously researched. The investigation into campaign spending continues."

Watch Mr Goldsmith defend his spending live on air, at 7pm tonight.