The Government's current commitment to defence spending is "simply not enough", ministers have been warned.
Conservative MPs called on the Government to increase defence spending to 3% of Gross Domestic Product (GDP) by 2030.
Former Cabinet minister Simon Clarke was joined by South Dorset MP Richard Drax in calling for an increase to the defence budget, as MPs debated the Autumn Statement.
In the statement, Chancellor Jeremy Hunt said he will maintain the defence budget at at least 2% of GDP.
Ahead of the statement, the Prime Minister was reticent to commit to a promise from his predecessor Liz Truss to raise defence spending to 3% of GDP, compared to the Nato minimum of 2.5%.
Mr Clarke, an ally of Ms Truss, told the Commons: "The former prime minister committed that we would spend 3% of our GDP on defence by 2030. And I believe that is a pledge that should be honoured."
"I'd also of course want to put on record just how strongly I would oppose any move to a Swiss-style relationship with the European Union, which I think… the Prime Minister has addressed decisively today," he told MPs.
Mr Drax meanwhile told MPs: "Worryingly, where money is needed, for defence, as a war rages in Europe, there’s to be yet another review, leaving the budget at an inexcusable 2% of GDP."
He had earlier said: "2% for defence is simply not enough. 3% is far nearer the target. It was 5% in my day and all the kit is much more expensive. So 3% is the amount that we need to spend.
"Will he just tell the House when are we going to really look at this? I believe there is going to be another review of the (integrated) review.
"When is that going to take place and will we have the Government's final decision on what it is going to spend on our Armed Forces?"
Treasury minister John Glen replied: "The integrated review is under review at this time. That needs to be done urgently, I think in the next three or four months, in order that we can come to an assessment of what that means for our defence spending.
"But I would say as I know he will know, that we did frontload a significant increase in the defence budget over this spending period of £24bn and I would work on the basis that while it must be our top priority, it must be based on an assessment on the need, and an updated assessment of which there has been a lot of changes in very recent times."