The execution, called "delivery", plays on the meaning of the word "cold".
Breaking on Friday, it is the first in a series of ads that will run until March 2004 showing cruel or harsh scenarios.
In the opening scene, a man is encouraging his wife as she gives birth.
He says: "That's it love, breathe. Big push now, and breathe. Yep, you're doing great. Yeah, I can see the head too."
The camera pans back and it becomes apparent the proud father is standing in a bar with his friend, talking into his mobile phone. He slurps from a pint of Carling Extra Cold before offering: "One big push love, running low on battery."
The endline reads: "Carling Extra Cold. It's Carling even colder."
Leith launched a poster campaign in London, Edinburgh and Glasgow back in June to first promote the Extra Cold variant.
Des Johnson, the brand director on Carling, said: "We've had a great response to the Carling Extra Cold product and advertising launch in the South East. Going national and being the first to do so is a nice way to close 2003. We'll be starting 2004 with the second in the campaign."
The television spot was written by John Messum and art directed by Simon Bere. The director was Graham Fink through Thefinktank.
Media planning and buying for the campaign was through Vizeum.