The International Development Secretary was in conversation with Institute for Economic Affairs (IEA) director Mark Littlewood in a well-attended meeting set up by the IEA in partnership with the Taxpayers’ Alliance.
Mr Littlewood asked her whether the government would slash public spending by up to half.
He proposed that the current rate of government spending, which is around 40 per cent of GDP, should come down to around 20 per cent.
Ms Patel would not put a figure on the reduction she wanted, but suggested that 20 years of greater cuts were needed.
She said that current spending was influenced by “the expectations of the British electorate” but added that these expectations could not be met.
Ms Patel said: “You know, we should be pretty clear we are promising a whole range of things to the electorate which you know today may not be sustainable — in fact which clearly aren’t going to be sustainable in five, 10, 15, 20 years’ time."