 On 4 December 2006, then Prime Minister Tony Blair revealed plans to spend up to £20 billion on a new generation of ballistic missile submarines to replace the "Vanguard" class.In order to reduce costs and show Britain's commitment to the Non-Proliferation Treaty, Blair suggested that submarine numbers could be cut from four to three, while the number of nuclear warheads would be cut by 20% to 160.On 23 September 2009, then Prime Minister Gordon Brown confirmed that this reduction to three submarines was still under consideration.