Tom Tugendhat has refused to say whether Downing Street signed off on his article calling for defence spending to be boosted as he renewed the appeal for an increase “now, as soon as possible”.

The security minister had last week joined Foreign Office minister Anne-Marie Trevelyan in breaking cover to say the UK must “lead the way” and invest at a “much greater pace”.

It followed criticism of Jeremy Hunt’s Budget for failing to raise defence spending, with the Chancellor saying it would be increased to 2.5% “as soon as economic conditions allow.”

During broadcast interviews on Monday, Mr Tugendhat declined to say whether Downing Street had cleared the article but renewed his call for urgency.

He told Sky News: “I want to achieve 2.5% now, you know, as soon as possible.

“First step to do is to get to the 2.5%, and then we’ll have to adjust as the challenges we face evolve.”

Asked by Ed Balls, a former New Labour minister, on ITV’s Good Morning Britain whether he had to get the article cleared by Number 10, Mr Tugendhat said: “Ed, did you have to clear everything through Labour? You probably did, actually, have to clear everything through Peter Mandelson, didn’t you?

“Probably how your Labour Party worked, where everything was so tightly controlled.”

In a highly unusual intervention from two serving ministers last week, Mr Tugendhat and Ms Trevelyan said the global risk posed by countries including Russia and China meant there was no time for delay.

“The sad truth is that the world is no longer benign,” they said.

“Protecting ourselves requires investment. And effective investment means that our industrial complex must grow and strengthen at much greater pace than at present.”

In the Budget, Jeremy Hunt said “our spending will rise to 2.5% as soon as economic conditions allow”, but there was no detail of how that would happen.

The article by Ms Trevelyan and Mr Tugendhat was not required to be cleared by No 10 because it is a social media post and it is also in line with Government policy on increasing spending to 2.5%.

However, it is a very visible sign of unease within the Tory ranks about the state of the defence budget.

Asked whether Number 10 had approved the article, Downing Street said later on Monday it “wouldn’t expect” to sign off on “social media posts which are in line with previously announced and agreed Government policy”.

“The Prime Minister agrees with his ministers in the importance of investing in defence. It’s exactly why the Government has overseen the largest sustained defence spending increase since the end of the Cold War,” Mr Sunak’s official spokesman said.

The Commons’ spending watchdog warned on Friday that the Ministry of Defence has no credible plan to fund the armed forces the Government wants, leaving the UK increasingly forced to rely on its allies.

The gap between the MoD’s budget and the cost of the UK’s desired military capabilities has ballooned to £16.9 billion, its largest deficit ever, despite an injection of £46.3 billion over the next 10 years, the watchdog said.

But the influential Public Accounts Committee (PAC) warned that the real deficit could be closer to £29 billion as some parts of the armed forces only included capabilities that were affordable rather than all those the Government had requested.

Ms Trevelyan, the Indo-Pacific minister, and Mr Tugendhat were both concerned about the level of defence spending needed to respond to China’s increasingly assertive global role.

They said: “It’s clear to us that the UK needs to lead the way in increasing our own domestic defence and security spending commitments to 2.5% and beyond.

“Former defence secretary Ben Wallace and prime minister Boris Johnson made inroads into growing our defence budgets, which had been shrinking in real terms for years, but that only filled the hole. Now we need growth.”

In a Sunday Times interview, Mr Sunak defended his record on funding the military.

“I would just point to our record here as chancellor when I oversaw the largest increase in the defence budget since the end of the Cold War with a £24 billion uplift,” he said.

“The whole point is, we recognised that the world that we’re living in was becoming more dangerous, and we had to invest more to protect the country against that.”