Ben Wallace has revealed that he asked Rishi Sunak to spend £2.3 billion more on military support for Ukraine before departing as defence secretary.

Writing for The Telegraph, Mr Wallace said the UK had been overtaken by Germany as the biggest European military donor to Ukraine. His intervention will increase pressure on the Prime Minister to spend more money supporting Kyiv against the Russian invasion.

Another £2.3 billion would be a 50 per cent increase on how much the UK has committed so far, but no decision on next year’s spending has yet been announced.

Whitehall debates about previous Ukraine funding have resulted in clashes between the Ministry of Defence and the Treasury, which Mr Sunak headed until July last year.

On Sunday, Joe Biden, the US president, moved to persuade Republican allies of Donald Trump to stop blocking more aid to Ukraine in a sign of splits in the West.

Divisions over defence emerged on the opening day of the Conservative Party conference in Manchester, with Mr Sunak playing down the prospect of UK military instructors being deployed in Ukraine after Grant Shapps, the new Defence Secretary, had floated the idea.

Mr Wallace, who stepped down as defence secretary in September, wrote: “Before I left office, I asked the PM to match or increase the £2.3 billion for Ukraine to add to the £4.6 billion we have spent already. The UK is no longer the biggest European donor to Ukraine – Germany is.

“This war can be won. Vladimir Putin is failing. Just as the human emotion drives Ukraine to success, it is also the inescapable flaw in Putin and his criminal regime. Romance, ego and revenge drove Putin to cross into Ukraine, and it will be his undoing.”