Ukraine's president Volodymyr Zelenskiy said he was "very happy" that Boris Johnson was still the British prime minister at a Tuesday online event.
"I'm glad we haven't lost a very important ally, this is great news," he said over video link at the event hosted by Financial Times Live.
Mr Johnson narrowly survived a confidence vote of his Conservative Party lawmakers on Monday.
The Ukrainian president called Mr Johnson a “true friend of Ukraine” as he spoke over video link.
Mr Zelenskiy told the newspaper: “I am very happy about this. Boris Johnson is a true friend of Ukraine.
“I regard him as our ally, and Great Britain as a great ally.”
Boris is very concrete in supporting Ukraine
Speaking through a translator, Mr Zelenskiy also said: “Boris is supporting us. Boris is very concrete in supporting Ukraine.
“I do not know who was responsible for this decision yesterday, but I’m glad we have not lost a very important ally. This is great news. That is all I can say.”
The prime minister’s official spokesman said: “The Prime Minister enjoys a very close relationship with President Zelensky.
“He believes it is vital to how the UK is able to adapt and support Ukraine in this fast-moving situation.”
The relationship “benefits both the Ukrainian people in being able to be responsive to the support they need but also to ensure the UK is at the forefront of providing that support”.
In a Cabinet meeting on Tuesday, Mr Johnson reiterated the UK’s support for Ukraine.
He also said it was vital that Mr Zelenskiy was not pressured into accepting a bad peace and that the world must avoid any outcome where Russian president Vladimir Putin’s aggression appears to have paid off.
The UK prime minister won 211 votes on Monday night, but a significant minority of 148 Tory MPs voted to usurp him and several have said his days in the role are now numbered.
