Deep cuts to the defence budget will see the Royal Navy's flagship aircraft carrier, HMS Ark Royal, and its fleet of Harrier jets scrapped "with immediate effect", Government sources have said.
The move is among wide-ranging measures to be unveiled by Prime Minister David Cameron on Tuesday as part of the military's share of the Coalition's severe public spending squeeze.
He is also expected to confirm that the strategic defence and security review (SDSR) has concluded that the renewal of the Trident nuclear deterrent will be delayed.
The immediate axing of HMS Ark Royal will leave the UK without an aircraft carrier capable of flying jets for around a decade while two new vessels are built at a cost of £5.2 billion. That project was spared the axe after it was found abandoning the contract - with one of the two already under construction - would end up costing the taxpayer more.
Although the first is set to come into service in 2016, converting it to allow it to be used by jets from allied nations could take several years. Neither will be able to be used for British military jets until 2020 and one could yet be mothballed and possibly sold under future options still being looked at by the military.
Defence Secretary Liam Fox has insisted the long gap in Britain's aircraft carrier capability will not affect its defence abilities - despite warnings from former Navy chiefs.
But Mr Cameron was reported to have told the Cabinet it was one of the hardest decisions he had faced since becoming Prime Minister.
He earlier laid the ground for the reductions by signalling a shift in the UK's security priorities towards the threat of terrorism and cyber attacks.
Publishing a National Security Strategy Mr Cameron said the present defence and security structure was "woefully unsuitable for the world we live in today".
A large-scale conventional military attack was ranked only in the third tier of threats to the UK which Labour said was being used as "cover" for a "rushed" defence review.