Samantha Cameron made her election trail debut this week, accompanying her husband David Cameron on a visit to an inner city youth club.

But the clear star of the video – which can be seen on the Conservative Party website – is clear: Samantha's burgeoning tummy.

Asked if he has been giving his wife any tips on campaigning, Mr Cameron says: "She doesn't need any tips, she's eclipsing me completely."

Samantha, expecting her fourth child in July, says: "I think the bump is."

'Web Sam Cameron' is the first in a series of planned films leading up to the general election, which Gordon Brown has called for May 6.