Lord Cameron has warned the US Congress not to repeat the mistakes of the 1930s by blocking a multi-billion pound aid package for Ukraine.

The Foreign Secretary said the West must not “show the weakness displayed against Hitler”, in an unusually blunt intervention into American politics.

In an article for The Hill, an influential Washington newspaper read by Capitol Hill policymakers and insiders, he said approving the support for Kyiv was “a matter of global security”.

He made the remarks as he embarked on a three-day tour of EU nations on Wednesday to drum up extra financial and military backing for Ukraine.

A proposed US aid package worth $95 billion (£75 billion) passed the Senate, the upper chamber of Congress, by a 70-29 vote on Tuesday.

But the bill appears all but doomed in the House of Representatives, where Mike Johnson, the Republican speaker, has refused to bring it to the floor.

Republican members, backed by Donald Trump, have refused to support the legislation until action is taken to boost security at the US-Mexico border.

Lord Cameron’s article will be seen as a direct challenge to supporters of Mr Trump, who are holding up the package for domestic reasons.

In it, he said the West faced “a simple test” of will against Vladimir Putin, who thinks he can outlast the US and its allies as “he believes we are weak”.

“As Congress debates and votes on this funding package for Ukraine, I am going to drop all diplomatic niceties. I urge Congress to pass it,” he wrote.

“I believe our joint history shows the folly of giving in to tyrants in Europe who believe in redrawing boundaries by force.

“I do not want us to show the weakness displayed against Hitler in the 1930s. He came back for more, costing us far more lives to stop his aggression.”

Lord Cameron said the West had displayed the same “weakness” when it failed to act after Russia invaded Georgia in 2008.

Meanwhile, the “uncertainty of the response” to the annexation of Crimea in 2014 had seen Putin “coming back to cost us far more with his aggression in 2022”.

“I want us to show the strength displayed since 2022, as the West has helped Ukrainians liberate half the territory seized by Putin, all without the loss of any Nato service personnel,” he wrote.

The Foreign Secretary suggested the West was underestimating its power to stop Russia, arguing that “we have the resources, the economic might, the expertise”.

He said the Kremlin had failed to act on previous support for Ukraine, such as the provision of tanks and long-range missiles, despite threatening retaliatory action.

“We have proved that the dangers of escalation are illusory,” he said. “Each time Putin has rattled his saber about escalation - and each time it has been empty rhetoric.

“Our economic strength outweighs Russia’s by a factor of around 25 to one. They are having to turn to Pyongyang for help. All we need to do is make our strength pay.”

He added: “It goes to the heart of what both sides of the aisle stand for. What both our countries stand for. We fight aggression.

“We stand up for freedom. We stick by our friends. We show this dangerous, uncertain world that we are unbending in our will. And we win.”

His intervention comes amid concerns within Downing Street and other European capitals that “war fatigue” is setting in, allowing Putin to outwait the West.

The EU passed its own €50bn (£43bn) aid package for Kyiv earlier this month, but only after months of internal wrangling sparked by Hungary.

Rishi Sunak announced last month that he will provide £2.5bn next year, taking the UK’s total financial and military aid up to almost £12bn since Russia’s invasion.

Lord Cameron warned that a failure to sustain support for Ukraine would embolden adversaries including China and Iran who are “watching” events closely.

He said: “America is strong enough to both protect itself at home and recognize that threats in Europe or Asia affect its own security. I for one would like Beijing and Tehran to see that.”

Mr Johnson blocked a vote on the aid package on Tuesday, telling reporters afterwards he would not allow one until his concerns were addressed.

Support for Ukraine has been controversial among some Republicans, with Mr Trump using it as a campaigning issue against Joe Biden ahead of November’s election.

The party has argued that the Democrats should take action to clamp down on illegal migration from Mexico before sending more taxpayers’ money abroad.

Mr Biden hit back angrily at Mr Johnson on Wednesday, accusing him and his party of putting politics above America’s national security.

Last week, the Republican speaker blocked a bill which the Democrats described as the “toughest, fairest border security legislation in decades”.

White House spokesman Andrew Bates said: “House Republicans are yet again putting politics ahead of national security - siding with Donald Trump, Vladimir Putin and Tehran against America’s defence industrial base, against Nato, against Ukraine and against our interests in the Indo-Pacific.

“The American people see through congressional Republicans’ elevation of their personal politics over the safety of the country. It’s time for the speaker to allow a vote.”