A key government adviser will accuse the UK's leaders of "corrosive complacency" towards defence and warn the country's security is "in peril".

Lord George Robertson, the former Nato secretary general who wrote the government's Strategic Defence Review (SDR), will use a speech later on Tuesday to accuse "non-military experts in the Treasury" of "vandalism".

The government has promised to publish a 10-year defence investment plan to fund the SDR's vision but it has been repeatedly delayed.

A government spokesperson said the SDR was "backed by the largest sustained increase in defence spending since the Cold War, with a total of over £270 billion being invested across this Parliament".

In a directly political intervention, Lord Robertson will warn: "We cannot defend Britain with an ever-expanding welfare budget."

In a speech in Salisbury, the former Labour defence secretary will say: "We are underprepared. We are underinsured. We are under attack. We are not safe . . . Britain's national security and safety is in peril."

He will add: "There is a corrosive complacency today in Britain's political leadership. Lip service is paid to the risks, the threats, the bright red signals of danger - but even a promised national conversation about defence can't be started."

The Prime Minister, Sir Keir Starmer, previously said the investment plan was on his desk and was being "finalised".

A defence official highlighted the government's target to spend 3% of GDP on defence by the end of the next parliament.

A government spokesperson said: "We are delivering on the Strategic Defence Review to meet the threats we face."

Following Russia's invasion of Ukraine and the re-election of US President Donald Trump, the UK, along with other Nato countries, has come under pressure to boost its defence spending.

The head of the British military told the BBC last month he rejected accusations that the UK had been ill-prepared for the current conflict in the Middle East, which began on 28 February with a joint US-Israeli attack on Iran.

Chief of the Defence Staff Sir Richard Knighton said it was "probably the most dangerous time of the last 30 years".

Some had questioned the UK's response, in particular around the sending of a Royal Navy ship to Cyprus to protect the UK military base, RAF Akrotiri, which was targeted by a drone.

The US president says Nato "wasn't there when we needed them" during the Iran war.

An MP welcomes the investment but says more needs to be done so industry can stay afloat.

Germany once terrorised Europe, but now Europe is welcoming a resurgent German military.

Exercise Cobra Warrior sees RAF, German and Polish fighter pilots training at RAF Waddington.

European leaders are hesitant to help Trump secure the Strait of Hormuz, but they know inaction on the Iran war is not really an option.