Military reforms in the UK could transfer operational command of the Royal Marines to the British Army.
The proposed restructuring plan would reduce eight brigades of land forces to five, a slash of up to 30,000 troops and give control of the marines to the British Army, according to the Financial Times.
New overhaul of armed forces could also combine the Royal Marine corps into a single expeditionary brigade with the paras.
The British Army has plans to cut its heavy armour brigades but not before a withdrawal from Afghanistan, the source said.
The Royal Marines have been under the command and control of the UK Royal Navy since 1755.