The Ministry of Defence (MoD) is facing a £28 billion funding shortfall over the next four years, Britain’s most senior military chief has warned.

Despite plans to increase defence spending, senior figures are preparing for significant cuts to the armed forces.

Sir Keir Starmer confirmed this week that UK troops could be stationed in Ukraine if a peace deal is agreed.

Tensions between London and Moscow continue to escalate, and the UK’s decision to join a US-led mission to seize a Russian-flagged tanker has done little to ease relations.

The Russian foreign ministry accused Britain of “maritime piracy” after the MoD vowed to continue targeting President Vladimir Putin’s so-called shadow fleet.

On Thursday, it emerged that a Russian “zombie” tanker was transiting the English Channel, prompting Defence Secretary John Healey to reiterate his commitment to step up action against such vessels.

Britain and France also unveiled plans this week, as part of the “coalition of the willing”, to deploy a multinational force to Ukraine in the event of a ceasefire.

Russia warned that any western troops sent to Ukraine would be considered “legitimate combat targets”.

Sir Keir told President Trump on Wednesday about the threat posed by an “increasingly aggressive” Russia in the “high north”, saying more could be done to protect the region, although European allies had already “stepped up”.

However, according to The Times, the internal mood at the MoD does not reflect the Government’s tough public rhetoric.

A source said Air Chief Marshal Sir Richard Knighton, the Chief of the Defence Staff, delivered a stark assessment of the department’s finances to the Prime Minister in a pre-Christmas meeting.

Mr Starmer was said to be frustrated, having believed that the recent Strategic Defence Review (SDR) had been fully costed.

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He instructed officials to rework the Defence Investment Plan (DIP), which will outline how the SDR is delivered. The document had been due for publication before Christmas but was quietly delayed.

The Prime Minister is said to be willing to provide additional funding in the near term.

A military source told The Times: “You need to look at big-ticket items to cut. Ministers have to make big decisions about big things.”

The British Army is thought to be the worst affected by the department’s financial pressures.

One project that could be scaled back is the £6.3 billion Ajax armoured vehicle programme, despite Sir Keir viewing it as central to his plans to modernise the force.

An MoD spokeswoman said: “The UK defence budget is rising to record levels as this Government delivers the biggest boost to defence spending since the Cold War, totalling £270 billion over this parliament alone.

“Demands on defence are increasing, with growing Russian aggression, higher operational requirements and preparations for a potential Ukraine deployment.”