In his first major speech since returning to the government, the former British premier will on Thursday urge NATO allies to deliver on a pledge to spend 2% of economic output on defence, and then increase expenditure to 2.5%, according to remarks briefed by the Foreign Office.

He’s also set to warn that “doing too little, too late, only spurs an aggressor on”.

“I see too many examples in this job of this lesson not having been learned,” Cameron warns in his speech at the National Cyber Security Centre. “While many countries have criticised the Houthi attacks, it is only the US and Britain that have been willing and able to step up and strike back at them. Or defence spend in Europe, where still some seem unwilling to invest, even as war rages on our continent.”

As concern grows about the rising risk of Russia’s war with Ukraine drawing in the West, Cameron’s remarks are a barb aimed at NATO nations that still fall short of the defence spending promise a decade after making it. 

Though Russia’s invasion of Ukraine spurred NATO to increase efforts to ramp up defence spending, countries including Canada, Spain and Italy are struggling to get to the 2% target. Germany, Europe’s biggest economy, has only recently met the goal for the first time.

Prime Minister Rishi Sunak’s UK government, for its part, has vowed to increase spending to 2.5% of GDP by 2030. 

“We are in a battle of wills. We all must prove our adversaries wrong – Britain, and our allies and partners around the world,” Cameron will say. “This cannot go on. We need to be tougher and more assertive.”