Sir Keir Starmer has vowed during a visit to Kyiv that the UK’s commitment to supporting Ukraine in its struggle against Russia would “remain the same” if he becomes prime minister.

The Labour leader also said there “has to be justice” for war crimes against the Ukrainian people as he visited areas that Russian president Vladimir Putin’s troops previously turned into conflict zones.

Sir Keir is in the war-torn country in eastern Europe, where he is expected to meet Ukrainian president Volodymyr Zelensky.

It follows a momentous visit by Mr Zelensky to Britain last week during which he implored Prime Minister Rishi Sunak to hand over fighter jets for his air force as Ukraine prepares to counter an expected Russian spring offensive.

During his visit on Thursday, Sir Keir spoke to reporters in Irpin, a Kyiv suburb where heavy fighting took place in the first months of Moscow’s invasion — a bloody conflict which is only days away from its first anniversary.

With Labour well in front of Mr Sunak’s Conservatives in most national opinion polls, Sir Keir could be walking through the black door of 10 Downing Street as Britain’s new leader after the next general election.

He stressed that his party was committed to Mr Zelensky and Kyiv’s cause.

“Should there be an election next year and a change of government, the position on Ukraine will remain the same,” he vowed.

“It’s very important for me to be here in Ukraine with the people of Ukraine, making it clear that support for Ukraine in the United Kingdom is united.

Ukrainian President Volodymyr Zelensky visit to UK
Ukrainian president Volodymyr Zelensky was in the UK last week (Aaron Chown/PA)

“Throughout the conflict, the Labour party has stood united with the Government in the United Kingdom to show our support for Ukraine”

Before meeting Mr Zelensky, the former director of public prosecutions will visit Bucha, an area where war crimes were allegedly carried out by occupying Russian troops.

The Opposition leader said he wanted to show support for Ukraine’s calls for justice and reparations for Russian actions during the war.

Sir Keir told reporters: “It’s incredible to see the evidence of atrocities that I’ve seen this morning.

“Photographs of civilians in the outskirts of Kyiv blindfolded, with their arms tied behind their back.

“There has to be justice for this. There has to be justice in The Hague and there has to be proper reparation in the rebuilding of Ukraine.”