The Royal Navy could be stripped of its ability to attack enemy-held beaches under cost-cutting plans, it has been reported.

The navy’s two amphibious assault ships, HMS Albion and HMS Bulwark, could be taken out of service in a new round of cuts to the armed forces, the BBC’s Newsnight said on Thursday.

It said such a move, which the Ministry of Defence described as “pure speculation”, would save money and free up crew for the two new aircraft carriers, HMS Queen Elizabeth and HMS Prince of Wales.

It comes days after Michael Fallon, the defence secretary, used a speech at the Conservative party conference to call for an increase in defence funding as his ministry announced a £1bn support package for the Royal Navy fleet.

Newsnight reported that the plan, coupled with the loss of 1,000 Royal Marines, had alarmed senior commando officers. If confirmed, the loss of Albion, a former flagship of the Royal Navy, and Bulwark would leave the Navy without a dedicated amphibious assault ship.

Beach landings in countries and areas where the enemy controls the harbours have been used in many modern conflicts, including D-day during the second world war and the Falklands war.

Fallon said in his speech that the armed forces must “modernise” the way they worked “as we grow our defence budget”.

He said that as threats intensify, his department was “now looking right across government to make sure we are doing enough, spending enough, to properly protect our country against all of those threats – cyber, hybrid warfare, rogue states, terrorist attacks”, adding: “Spending 2% of GDP on defence is the minimum Nato commitment. We meet it but we should always aim to do better still.”

An MoD spokesman said: “In the face of ever-changing threats, we are contributing to the cross-government review of national security capabilities and looking at how we best spend our rising defence budget to support that. No decisions have yet been made and at this stage, any discussion of the options is pure speculation.”