A £1.2 billion contract has been awarded to build the Royal Navy's new hunter-killer submarine HMS Audacious.

The Ministry of Defence (MoD) also announced that a further £1.5 billion has been committed to the remaining three submarines in the class.

The £1.2 billion contract with BAE Systems will safeguard 3,000 skilled jobs at Barrow in Cumbria.

Audacious is the fourth of seven Astute Class submarines being built for the Royal Navy. They are the most technologically advanced the Royal Navy has ever sent to sea and will progressively replace the Trafalgar Class currently in service.

The first two boats, Astute and Ambush, are currently undergoing sea trials to rigorously test their systems. The third boat, Artful, is reaching the final stages of her construction at Barrow shipyard. Early work has been started on boat five, named Anson, while preparation has begun on as yet unnamed boats six and seven.

Last month it emerged that Astute encountered a flooding problem during sea trials, forcing the nuclear-powered attack vessel to resurface after it let in tens of litres of water. Electrical switchboards were also found to be fitted incorrectly while concerns emerged about the accuracy of nuclear reactor monitoring instruments during testing last year.

The MoD said electrical switchboards on board Astute, which ran aground near Skye off the west coast of Scotland in 2010, had not been fitted to Naval Engineering Standards and have since been reinstalled.

Defence Secretary Philip Hammond said: "This funding demonstrates our commitment not only to a key Royal Navy capability, but also to the submarine industry in Barrow, which will play a vital role in Britain's defence for decades to come."

BAE Systems Maritime submarines managing director John Hudson said: "This is a very significant milestone for the company as it provides increased stability for the remainder of the programme.

"The Astute class will deliver to the Royal Navy a fantastic attack submarine capability and both HMS Astute and Ambush are currently demonstrating this while on their sea trials. Audacious, and the rest of the submarines in the Astute class, will eventually complement those already at sea."

The Press Association, photo by Defence Images