Prime Minister Sir Keir Starmer has expressed support for Volodymyr Zelensky as a “democratically elected leader” after Donald Trump described the Ukrainian president as a “dictator”.

Sir Keir spoke to Zelensky on the phone on Wednesday evening and said it was “perfectly reasonable” for Ukraine to “suspend elections during war time as the UK did during World War II”, Downing Street said.

The call came after Trump criticised Zelensky, saying he had done a “terrible job” and claiming “he refuses to have elections” in Ukraine as a condition of a deal to end the war.

Zelensky had accused Trump of living in a Russian “disinformation space” after the US president appeared to blame Ukraine for starting the war in the country.

A Downing Street spokesperson said Sir Keir “stressed the need for everyone to work together” in his phone call with the Ukrainian president.

“The prime minister expressed his support for President Zelensky as Ukraine’s democratically elected leader and said that it was perfectly reasonable to suspend elections during war time as the UK did during World War II,” the spokesperson said.

“The prime minister reiterated his support for the US-led efforts to get a lasting peace in Ukraine that deterred Russia from any future aggression.”

Following the phone call, Zelensky said the UK’s role “in fortifying Europe’s defence and security is important for us”.

The Ukrainian leader said he and Sir Keir discussed “upcoming plans and opportunities”, adding that the “UK’s support matters indeed, and we will never forget the respect the British people have shown for Ukraine and our citizens”.

Conservative leader Kemi Badenoch has also defended the Ukrainian leader.

In a post on X, Badenoch said Zelensky was “the democratically elected leader of Ukraine who bravely stood up to Putin’s illegal invasion”.

But Badenoch said Trump was “right that Europe needs to pull its weight” and called on Sir Keir to “get on a plane to Washington and show some leadership”.

The row between Trump and Zelensky has increased the political jeopardy for Sir Keir, ahead of a high-stakes meeting with the US president next week.

The prime minister will travel to Washington DC for his first in-person meeting with Trump as he seeks to influence the American approach to ending the war in Ukraine.

Sir Keir has said he wants to use his meeting with Trump next week to discuss a “US backstop” that he says is necessary to deter Russia from attacking its neighbour again.

The prime minister has said he would be prepared to deploy British troops to Ukraine to help guarantee its security as part of a peace deal.

Speaking to BBC Newsnight, Andrei Kelin, the Russian ambassador to the UK, said Moscow would not accept troops from the UK or other European nations in Ukraine, even if President Trump approved it.

Kelin also questioned whether there could be a potential peace agreement without fresh elections in Ukraine.

Zelensky won a five-year term in 2019 and has remained in office because elections have been suspended since martial law was declared after Russia’s invasion.

Asked if Russia would give back some of the territory it had seized from Ukraine, Kelin said: “Why should we? We have liberated these territories, upon which Russian people are living for centuries.”

The UK and other European nations have been scrambling to respond to this week’s rapid developments, almost three years after Russia launched its full-scale invasion of Ukraine.

The week started with diplomats from the US and Russian meeting in Saudi Arabia for talks aimed at ending the war.

The US was accused of sidelining European leaders, including Zelensky, by not inviting them.

Then on Tuesday, President Trump appeared to blame Ukraine for the war and suggested the Zelensky’s popularity rating was as low as 4%.

It’s unclear what source the president was citing as he didn’t provide evidence. A survey conducted this month found that 57% of Ukrainians said they trusted the president, according to the Ukraine-based Kyiv International Institute of Sociology.

In his remarks on Wednesday, Trump warned Zelensky that “he is not going to have a country left” if he did not make peace.

In the UK, Liberal Democrat leader Sir Ed Davey said calling Zelensky a dictator “must be where the line is drawn”.

He wrote on X: “It is my sincere hope that the whole political spectrum in the United Kingdom will speak with one voice in opposition to Trump’s lies.”

Tory MP and former cabinet minister James Cleverly said Trump was wrong about Zelensky and urged Foreign Secretary David Lammy to “say so”, adding “his silence is deafening”.

“The UK & USA must send the message that we don’t let tyrants win!,” he posted.

Former Prime Minister Boris Johnson has also waded into the war of words, posting to say “of course Ukraine didn’t start the war”.

He added: “Trump’s statements are not intended to be historically accurate but to shock Europeans into action.”

Earlier, UK Defence Secretary John Healey visited Norway’s border with Russia with Norwegian defence minister Tore Sandvik.

Asked whether the UK agreed with Trump’s suggestion that Ukraine “started it”, Healey told reporters: “Three years ago, one country illegally invaded another, and since then the Ukrainians have been fighting for their freedom.

“They’ve been fighting for their future, and they still are.

“So whilst all the focus may be on talks, not even negotiations, our concern as defence ministers is that we’re not jeopardising the peace by forgetting about the war.”