The Prime Minister's assertion in last week's Conservative Party political broadcast sparked a furious complaint by Labour, which described his comments as "deliberately misleading", as the debt was actually rising.
Chair of the UK Statistics Authority Andrew Dilnot confirmed yesterday that public sector net debt has risen from £811 billion in 2010, when the coalition took office, to £1.1 trillion at the end of last year.
Responding to Labour's complaint, Mr Dilnot said it was important politicians distinguished correctly between accumulated debt, and annual public sector borrowing – which has come down.
"It is clearly important for all parties to public debate in this area to understand the relevant statistical definitions and to distinguish changes in the level of debt outstanding from changes in borrowing per period, and to reflect these in their communication of the statistical trends involved," he wrote.
"Public sector net debt is a measure of how much the UK public sector owes at a given time. Public sector net borrowing is the difference between total accrued receipts and total accrued (current and capital) expenditure over a specified period; this measure is frequently used by commentators to summarise the extent of any public sector deficit." He said he was sending a copy of the letter to Mr Cameron's chief of staff, Ed Llewellyn.