It was a bad day at the office or rather the radio station this week for the Green Party leader, Natalie Bennett, as she turned in a distinctly off-colour performance during her interview on LBC Radio. When asked about the party's policies, she appeared to struggle when attempting to answer basic questions that were directed at her, pausing and clearly unsure of her facts. In particular, she was unable to explain just where the finance would come from to pay for the ambitious house building programme that the party is advocating. She has subsequently apologised to party members for the below par display.

The radio interview on Tuesday with Nick Ferrari on the London-based national talk and phone-in radio station, formed part of the launch of the Green Party's election campaign in London. It was clearly an inauspicious beginning to what they hope will be a fruitful campaign, as their figurehead seemed at ease when asked to elaborate on some of their ideas.

When Ms Bennett was asked by Mr Ferrari about the party's plans to build 500,000 social rental homes, she explained that the funding would come from the removal of tax relief on mortgage interest for private landlords. When asked repeatedly to put a figure on the expected cash that would generate, she stumbled in response before vaguely uttering "that's part of the whole costing." More stalling for time and non-specific responses were also 'forthcoming', when she was asked about the overall cost that would be involved in building the homes, as she advised that "will be spelt out in our manifesto."

The interviewer was clearly unimpressed by her answers, claiming that she did not really know what the figure would be. That did at least prompt Ms Bennett to come up with a figure of £2.7bn for the total cost to build the homes. Showing an admirable grasp of basic maths, Mr Ferrari was at a loss as to how the figures stacked up, semi-jokingly replying: "What are they made of - plywood?" That further prompted the interviewee to attempt to clarify her answer by suggesting that the cost per home would be in the range of £60k.

Ms Bennett has since made her apologies to the members of the party for her "mental brain fade", but it will be a concern to them during such a high profile period in the run up to the UK general election in May. #Celebrities

At the official launch event held at the Royal Society of Arts in London, Ms Bennett felt more at ease as she insisted that her party's presence during the election would be the "biggest, boldest campaign ever." Much in line with the radio interview though, the launch was thin on substance as no specific policies were launched, as those will be signed off at a party meeting next month. That may have had much to do with her uncertain responses during the radio interview.