03/06/2015 10:37 BST | Updated 03/06/2015 10:59 BST

Watch David Cameron Encourage New MP to Run For Labour Leadership: 'Go For It'

David Cameron urged a newly elected Labour MP to run for leader of her party today and jokingly praised her for asking a question about fiscal responsibility.

Cat Smith, 29, who won the Lancaster and Fleetwood from the Conservatives in May, asked Cameron during prime minister's questions when he expected the United Kingdom to "regain its AAA credit rating".

In February 2013, the UK lost the premium credit rating for the first time since 1978. When he took office as chancellor in 2010, George Osborne said maintaining the AAA rating was his "first benchmark" of economic success.

The prime minister dodged the question today, but had some fun at Labour's expense. "If I might say, I think the first question she asks which is about fiscal responsibly and sustainability, I take that a s a sign of progress," he said.

"I would say to her, there's a leadership election on, throw your hat in the ring. In that one question she has made more sense than the rest of them put together. Got for it."

Ed Miliband's unexpected by overwhelming election defeat has been blamed by many on a belief that Labour lacks of economic credibility. A charge frequently exploited by the Conservatives.