The United States Ambassador to NATO, Matthew Whitaker, has stated that Britain is "incomplete" due to a lack of a credible plan to increase defense spending, a criticism delivered as a "humiliation" for the current government.

Whitaker, an ally of President Trump, urged ministers to "do their homework" and develop a strategy to raise defense expenditure to five percent of the Gross Domestic Product (GDP). He emphasized the need for the UK to become "more capable and more ready" for potential conflicts.

"Incomplete is the grade I would give them right now – because I think there is great capacity in the UK to spend more on defence, to become more capable," Whitaker told Sky News. He noted that while Britain has a history of a "strong and capable and ready defence apparatus," this is not the current reality.

"We're expecting them to do the things they need to do, long term to do their homework and to come up with a credible plan that by 2035 will get them to the five per cent," Whitaker added. "The UK is a serious ally. We want them to be more capable and more ready, and I think that they will be committed to that. But as of today, we're not quite there."

These remarks follow criticism of the UK's defense investment plan, published as one of the Prime Minister's final acts in office. The plan has been widely condemned for allegedly failing to address current threats, and it neglected to specify when defense spending would be raised to three percent of GDP, a level considered a minimum for national security.

In response, shadow defense secretary James Cartlidge stated that Labour's defense investment plan had "completely unravelled" and that "now even our closest allies are calling them out over it." He further claimed that the plan lacks funding and that "Keir Starmer is not willing to take the tough decisions needed to keep the country safe."

Whitaker suggested that economic growth is the "simple solution" to funding increased defense spending. "The equation is quite simple: you can either grow your economy, which will create more room to spend money on defence, or you are going to have to make the difficult political choices," he said.

Whitaker also declined to endorse any reported ambitions of the UK leadership to succeed Mark Rutte as NATO secretary general, stating that such decisions would be considered in the future and that there would be "a lot of great candidates."