Funding for the armed forces should be on a par with the NHS, the defence minister has suggested.
Tobias Ellwood said he is “deeply concerned” that Britain is taking its security for granted as the world gets more dangerous.
Amid suggestions the Ministry of Defence (MoD) faces a black hole of at least £20 billion over the next decade, the minister said spending on the armed forces must increase.
In a report published by the Public Accounts Committee last week, MPs warned that the MoD “simply does not have enough money to buy all the equipment it needs”.
On Tuesday, the US ambassador to London said Britain must consider how it wants to be perceived by America and its adversaries while weighing up how it spends its national budget.
Mr Ellwood said: “You go back to the 1970s and 1980s and there was a parity between defence spending compared with health and education – and today we have dropped back to 2%.
“The Government often does what people call for. If people call for more money for schools and hospitals, that is often where the money then flows. It is important we raise the profile of the dangers of reducing our defence posture. Once you lose it, you will never get it back.
“I am deeply concerned we have a nation which is fully appreciative of our armed forces but which takes our security for granted.”
The former Army captain said countries like Russia and China are “rewriting the rule book” and Britain had to ensure it has the “full spectrum of capabilities”.
The UK would also have to decide “how you want to be perceived, by the US, but also by Russia and others”, he said.
Mr Johnson added: “Healthcare is always going to be an issue, education is always going to be an issue, transportation and infrastructure are always going to be issues, etc.
“But how important is it to defend yourself? I came over here … my mission is security and prosperity, and you really can’t have prosperity unless you have security.”
A Downing Street spokeswoman insisted that Mr Ellwood was not calling for defence spending to be the same as that on the NHS.
“He was talking about a time in history when the government did give parity to health and defence spending; he was not calling for that parity to be brought back,” the spokeswoman said.
“He was making the point that we mustn’t lose sight of a strong defence budget in the face of other challenges and of course the Prime Minister absolutely agrees with that, which is why we are the biggest defence spenders in Europe.”