Prime Minister Gordon Brown has told Liberal Democrat leader Nick Clegg to "get real" on the UK's need for a nuclear deterrent, during the prime ministerial debates.

The Lib Dems have ruled out the "like-for-like" replacement of Trident, the UK's nuclear weapons system, when it runs out in the 2020s.

Conservative leader David Cameron said he agreed with Gordon Brown that the Lib Dem's position was unviable.

Clip courtesy of Sky News Leaders' Debate