The British Army is to establish a new Special Operations Brigade to carry out missions in “high threat” environments overseas, the Ministry of Defence has announced.

Under the plans, four infantry battalions will be absorbed into a new Ranger Regiment enabling them to undertake roles traditionally carried out by Special Forces – the SAS and SBS.

Defence Secretary Ben Wallace said they would be at the forefront of a more “active and engaged” armed forces following the publication earlier this week of the Integrated Review of foreign and defence policy.

They will be routinely deployed around the world supporting allied nations in delivering defence and security.

A share of £120 million will be invested in the unit to enable to take part in “collective deterrence” such as training, advising, enabling and accompanying partner forces.

At the same time, a new Security Force Assistance Brigade will draw from specialised infantry units to provide further guidance and training to allied forces.

Mr Wallace said: “The best way to prevent conflict and deter our adversaries is to work alongside partners to strengthen their security and resilience.

“These Ranger battalions will be at the vanguard at a more active and engaged armed forces.”

The Chief of the General Staff, General Sir Mark Carleton-Smith, said the Special Operations Brigade was designed to operate alongside “both regular and irregular partners and proxies in high-threat and hostile environments”.

“The Army Ranger Regiment will be the vanguard of the Army’s global footprint,” he said.