Liberal Democrat MP Tessa Munt yesterday threatened to quit as a party whip over the replacement of Britain's nuclear weapons system.
The Wells MP was speaking at the Lib Dem Liverpool conference, as party members demanded a review of whether Trident should be renewed.
Armed Forces Minister Nick Harvey put himself on a collision course with Defence Secretary Liam Fox, when he said delaying a decision would not be significant.
As the Daily Press has reported, North Somerset MP Dr Fox will resign if the decision is put off, one of his closest allies has claimed.
Ms Munt won applause during an emergency debate on Trident when she said: "I'm a baby whip – but I've made it clear there are some things I fundamentally disagree with.
"If it has to come to it, I shall resign from being a whip because I feel so strongly."
She told delegates the cost of Trident must be compared with that of the housing, education, health and social care needs of the nation. We have the opportunity to decide what we want to do with the money we have. You're going to have the opportunity to persuade our MPs – that's how coalition works."
North Devon MP Mr Harvey hinted the Trident decision would not happen until after the 2015 General Election – and said it was important politically, not militarily.
"If it were to be delayed until just after the May 2015 election, it is of no great financial significance, it is of no great military significance, it is of no great industrial significance.
"But believe me, it is of profound political significance.
"Conservatives know that they are not going to be able to look to the Liberal Democrats to get that through Parliament, so the issue will be a hot potato for Labour."
Mr Harvey said the UK should not commit itself to "another Cold War-scale nuclear deterrent and take up that stance for another 40 years".