Boris Johnson has spoken to Volodymyr Zelensky and described the Ukrainian leader as a “hero”, after he resigned as Conservative leader.
Mr Zelensky is said to have thanked Mr Johnson for his “decisive action” to help Ukraine following the Russian invasion.
Mr Johnson said there is “unwavering cross-party” support in the UK for Ukraine, and he pledged defensive aid would continue for as long as needed.
During his resignation speech outside Number 10 earlier on Thursday, Mr Johnson said the UK’s support for Ukraine is one of the key achievements of his premiership.
He most recently visited Kyiv last month.
The call between the two leaders took place on Thursday afternoon.
A Downing Street spokeswoman said: “The Prime Minister highlighted the UK’s unwavering cross-party support for President Zelensky’s people, and said the UK would continue to supply vital defensive aid for as long as needed.
“The Prime Minister added that he would continue to work at pace with partners to try and end the grain blockade in the coming weeks.
“He thanked President Zelensky for everything he’s doing to stick up for freedom, for his friendship and for the kindness of the Ukrainian people.
“President Zelensky thanked the Prime Minister for his decisive action on Ukraine, and said the Ukrainian people were grateful for the UK’s efforts.
“The Prime Minister finished the call by praising President Zelensky, saying: ‘You’re a hero, everybody loves you’.”
During his speech outside Downing Street, Mr Johnson said: “Let me say now, to the people of Ukraine, that I know that we in the UK will continue to back your fight for freedom for as long as it takes.”
He also said he was “immensely proud” of his Government’s achievements, including “leading the West in standing up to (Russian President Vladimir) Putin’s aggression in Ukraine”.
As news of the Prime Minister’s departure broke, political figures in Ukraine paid tribute to him.
The UK has provided weapons and training to Ukraine, with military and financial aid stepping up after the invasion began on February 24.
Mykhailo Podolyak, an adviser to Mr Zelensky, tweeted his thanks to Mr Johnson, saying the PM had “always been at the forefront of supporting Ukraine”.
In a video posted on Twitter, he said the Prime Minister had “began to call a spade a spade” and emphasise the seriousness of the war with Russia to the international community.
Mr Podolyak said: “Today we have everything we need for the effective defence of our country.
“Weapons, partnership and coalition. Thanks to Mr Johnson, we understand that victory is a symbol for the future of Ukraine.
“Victory will be ours, because the civilised world is completely in pro-Ukrainian positions.”
Ukrainian MP Oleksiy Goncharenko also tweeted thanks to Mr Johnson.
He said: “Ukraine is infinitely grateful to you for everything you have done for us.
“You will forever remain in our history and will be involved in the future victory. Thank you.”
Ukrainian Internal Affairs Ministry adviser Anton Gerashchenko tweeted: “Boris Johnson, sir, you are a true friend of Ukraine.
“We are very grateful for your strong position in supporting Ukraine.
“We wish you strength and you are always welcome in our country.”
Earlier on Thursday, Defence Secretary Ben Wallace was asked if a change of leadership in the UK would affect the response to the war in Ukraine.
Speaking before the Prime Minister’s resignation statement, Mr Wallace said there was a cross-party consensus on Ukraine.
He said President Zelensky and Defence Minister Oleksii Reznikov both knew the UK is “full-square behind them”.
