The Conservatives are accusing Ed Miliband of preparing to "stab the United Kingdom in the back", trading away Britain's nuclear deterrent in order to secure power in a backroom deal with the Scottish Nationalists.
Trident became a major campaign bone of contention today, because of the SNP's declared determination to scrap the nuclear deterrent. Nicola Sturgeon has told ITV News it's a "blood red line" that cannot be crossed, in any future Parliamentary deal with the SNP.
From Faslane, ITV News correspondent Martin Geissler reports:
The main political parties are wrangling over whether the UK should spend billions renewing its nuclear deterrent.
If a difference of opinion on defence didn't get in the way of the current coalition - why would it be different for Labour and the SNP?