Defence Secretary Ben Wallace has piled pressure on Boris Johnson to pump extra cash into the military amid a Cabinet row.
Mr Wallace said funds allocated to the armed forces were not enough following Russia ’s invasion of Ukraine.
The Prime Minister, who today urged NATO allies to “dig deep” over funding, faces a growing Cabinet revolt over money for the forces.
Mr Wallace said while he had enough funding for the "here and now", extra investment was needed in the next Government spending round from the middle of the decade.
And he warned the threat from countries like Russia “is not likely to change for the rest of the decade”.
Mr Wallace said Russia’s nuclear threat has “been invoked at least 35 times by Putin”.
He told BBC Radio 4’s Today programme: “This rhetoric is starting to get more bellicose, more directed at different nations every time they say something or do something.
“I think you heard the Deputy of the Duma recently saying Britain would be first to be struck by Russia.”
Comparing Ukraine to Poland being invaded by the Nazis in 1939, he said: “Ukraine is a country that’s chosen to be westward facing, wants our values, shares our values, and is being brutally invaded by a country that plays no rule, doesn’t stick to the Geneva convention, that commits war crimes, rapes, pillage, that countryside we just saw yesterday, that horrendous strike on a shopping centre.”
Speaking to Sky News he added: “We were prepared to take certain vulnerabilities on board in the middle of the decade as we got rid of some equipment and re-equipped anew.
“I think the invasion of Russia into Ukraine has changed that.
“That is why I think discussions are so important for the middle-of-decade funding. In the here and now we are rightly set - the question is what happens in the middle of the decade.
“My settlement was done before Russia invaded Ukraine. Russia is very, very dangerous on the world stage.
“The world is less secure than it was two, three years ago and is not looking likely to change for the rest of the decade.
“That is the moment, in the middle of the decade, to say we should commit to increased funding."
Asked if it was true he wrote to the Prime Minister asking for a 20% hike he replied: “No”.
Asked how much he would like he replied: “How long is a piece of string?”
It came after reports Downing Street watered down a speech by Mr Wallace on defence spending yesterday.
The Defence Secretary had been due to say spending 2% of GDP on defence was outdated, according to The Telegraph.
Mr Wallace admitted some words in his speech were taken out by No10 - but insisted the Prime Minister was due to say them himself.
He told Sky News: “As Defence Secretary my most important target is remaining above 2% if not greater of GDP which is the main Nato benchmark.
“And I think it’s really important that we continue to commit to that, if not greater.”
It came as Boris Johnson said Vladimir Putin ’s invasion of Ukraine has backfired after NATO backed membership bids by Finland and Sweden.
Turkey dropped its opposition to the accession plans of Helsinki and Stockholm, in a historic move which paves the way for the alliance’s expansion.
Arriving at the NATO Summit in Madrid, Boris Johnson said: “If Vladimir Putin was hoping that he would be getting less NATO on his Western front as a result of his unprovoked illegal invasion of Ukraine, he’s been proved completely wrong. He is getting more NATO.”
Welcoming a “huge step forward for our alliance”, the Prime Minister added: “We’re going to be doing now is talking about what more we can do as an alliance to support the Ukrianians but what we also need to do to make that sure we think about the lessons of the last few months and the need for NATO to revise its posture on its eastern flank.”
