Police say the increase was planned before the girls were shot

Chief Inspector Tony Styles, who heads the firearms operations unit, said the increase had been planned for some time.

It will bring the total number of firearms officers in the region to more than 100.

Mr Styles said: "Given the size of the West Midlands and the number of incidents we are required to respond to, it is inevitable that the unit needed to increase.

He added: "We will be looking to recruit these additional officers over the next 12 months, but it takes time for them to go through the lengthy selection and training process."

Mr Styles said the move was not prompted by the fatal shooting of teenagers Letisha Shakespeare and Charlene Ellis in Birmingham on 2 January.

West Midlands Police currently operates three armed vehicles and organises armed escorts, security for VIP visits and planned operations in addition to responding to serious crimes.

The decision to expand the armed unit comes days before a national guns amnesty is planned.

The initiative, which is aimed at reducing the number of firearms on the streets, will be launched on Monday and run for a month.