The UK national debt

Hi,

Something is puzzling me. When Gordon Brown narrowly lost the UK election after the 2008 banking crisis, the Tory opposition ran on a fierce criticism of government borrowing. The national debt at that time was around £750 billion. Tory chancellor Osborne continued the incompetence meme against Labour and instituted 'austerity' in government finances. The result of this was an increase in the national debt to around £1.5 trillion at the time of Osborne's departure.

Now, the new Tory chancellor, Hammond, has told the Beeb that he intends to continue borrowing up to a notional limit of £2 trillion.

My question: If £750 billion of debt after a global banking crisis is incompetent, why is £2 trillion of debt after years of 'austerity' in government spending not incompetent?

D.