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.
The way the Conservatives' tried to nail the day's election agenda to the issue of Britain's nuclear deterrent has ended with Labour accusations that they'd descended into the politics of the gutter. The row was about the way the Defence Secretary, Michael Fallon, criticised the Labour leader Ed Miliband.
He said Mr Miliband has stabbed his brother David in the back to get the leadership and was ready to do the same to the United Kingdom over its security. He was claiming there could be some sort of deal with the SNP to scrap our nuclear submarines.
On the Conservative campaign trail ITV News' James Mates assesses the fall-out:
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?