American jets, such as these F-35s at RAF Lakenheath in Suffolk, are a common sight at British bases and given the funding gap that the military is struggling with they look unlikely to be heading home soon

The core plan for Britain’s armed forces will be revised after the election because of a funding crisis, The Times can reveal.

The unravelling of the 2015 defence review is a blow for Sir Michael Fallon, the defence secretary. Sources questioned whether he could remain in post after an anticipated Conservative election victory in June given the problems that he has presided over at the Ministry of Defence (MoD). They include:

• A lengthy delay in agreeing this year’s budget, which should have been finished in January but dragged into April. The Royal Navy had to receive hundreds of millions of pounds of extra cash to cover the cost of new warships and submarines. This impacted on funding for the army, the Royal Air Force