The defence secretary appears undeterred from his pursuit of a like-for-like renewal of Britain's nuclear deterrent, despite opposition from Liberal Democrats.
The junior coalition party is already credited with winning a delay in the final decision on Trident until after the next general election.
But yesterday Liam Fox announced the steel for the first new nuclear submarine was being ordered - because of the lengthy lead-in time required to ensure it is ready.
Today Dr Fox hardened his position still further by insisting that Britain could not maintain a credible deterrent with only three nuclear submarines, as opposed to the current four.
"If you reduce the number you take an increased risk in your ability to deploy that deterrent at all times," he told BBC Scotland.
"So at the moment the technology says four. That's something that can always be kept under review."
Last autumn saw the Lib Dem conference celebrate its achievement in delaying the 'main gate' decision on Trident until after May 2015.
Many party members are concerned that Dr Fox has pursued the nuclear deterrent regardless, however.
He added: "We are seeing other countries potentially trying to develop nuclear weapons. And we cannot gamble with Britain's future security."
His behaviour is prompting speculation from a number of quarters. Kate Hudson, general secretary of the Campaign for Nuclear Disarmament, fuelled Lib Dem fears by writing on the Lib Dem Voice blog: "It seems like a piece of double-dealing of the worst sort - that the government is saying one thing and doing another, pulling the wool over the eyes not only of the public, but of its Liberal Democrat supporters."
She suggested an alternative motive might be the Ministry of Defence "pursuing its own track, irrespective of the political agreement and process set out by the coalition government".
Lib Dems like Tom Brake have already begun expressing alarm. Mr Brake told the Evening Standard that the decision to order the super-strength steel yesterday was a "false start" and that Dr Fox had "jumped the gun".
"Clearly there is a commitment on behalf of the government to assess the value for money of the Trident replacement programme," he told the Evening Standard.
"This has got to happen before components of the system are being purchased."
Conservative backbenchers firmly approve of Dr Fox's actions, however.
Patrick Mercer told the same news newspaper: "This is a clear indication that he will not be distracted from his course from those who would be happy to leave the nation open to attack."