Speaking at a press conference in Berlin alongside Annalena Baerbock, the German foreign secretary, Lord Cameron said the crises needed to be in the “best possible place” by the time of the US election.
Lord Cameron has previously raised concerns about the commitment of Donald Trump and his Republican allies to the fight against Vladimir Putin.
Macron caused disquiet among many in Europe by refusing to rule out sending Western ground troops to Ukraine, pointing to Russia’s hardening stance. He then urged Ukraine’s allies not to be “cowards” in supporting the country to fight off the Russian invasion.
Some party leaders said Macron advocated a “no limits” approach to counter the Russian president as part of his theory of “strategic ambivalence” – keeping Moscow guessing.
Jordan Bardella, the president of the hard-Right National Rally (RN) party, said he had urged Macron “not to go to war with Russia”.
Threatening to send French soldiers “to fight a nuclear power like Russia is irresponsible and extremely dangerous for world peace”, he said.
Fabien Roussel, the Communist Party leader, said that he feared that Macron was “ready to engage in a bellicose escalation which would be very dangerous”.
Marine Tondelier, the leader of the Green Party, recounted Macron saying that Putin “obviously has no limits”.
She said it was “extremely worrying” to see the president tell the meeting that “we must show we have no limits” too.
‘I left even more worried’
Manuel Bompard, of the hard-Left France Unbowed party, added: “I arrived worried and I left even more worried.”
The Macron camp has made it clear that one aim of meeting the opposition was to “clarify” their position on Ukraine, notably that of the RN, which long admired the Putin administration before the war.
Prisca Thevenot, a government spokesman, said that it was “quite obvious” that the RN was not aligned with Macron’s call to do everything to ensure Russia’s defeat.
Gabriel Attal, the French prime minister, has accused the RN of “supporting Russia more than Ukraine”, even questioning whether “Vladimir Putin’s troops are not already in our country in the guise of Marine Le Pen’s party.
The RN is the largest opposition party in France’s lower house of parliament and leads the Macron alliance by a wide margin in European election polls ahead of the June 9 vote.
Reacting to the reports, Dmitry Peskov, a Kremlin spokesman, said on Thursday that Mr Macron “continues to raise the level of France’s direct involvement” in the war.