Defence Minister Tobias Ellwood is prepared to resign if cuts to the British Army take place.
The minister for Defence People and Veterans is understood to have concerns about proposals which could see the Army’s full-time strength reduced by 12,000 troops, to 70,000.
Mr Ellwood has allegedly shared his “deep discomfort” with colleagues about a list of cost-saving options faced by the Ministry of Defence, according to the Times newspaper.
A Whitehall source quoted by the newspaper said the Ministry of Defence was “beginning to try and push back” against the cuts.
Defence Secretary Gavin Williamson was said to be shocked by the “completely awful” headline proposals drawn up by military chiefs.
An MoD spokesman said: “We have the biggest defence budget in Europe and are one of very few countries to not only meet but exceed NATO’s 2% spending target”.
Former Army officer and Defence Select Committee member Johnny Mercer MP said the cost of the Trident nuclear deterrent should not be part of the MoD’s budget.
The Conservative MP said he was “advocating hard” for the cost of sustaining the continuous at-sea deterrent, which accounts for around 6% of the annual defence budget, to be borne centrally by the government.
Liberal Democrat defence spokesman Lord Campbell of Pittenweem said:
“Reducing the Army even further, cutting the Royal Marines and selling surface ships will fracture our defence capability.”
The MoD said no decisions had been made and dismissed reports about the options being considered as “speculation”.