Labour has complained to the statistics watchdog about a claim in David Cameron's conference speech that Britain is "paying down its debts".
In a letter to the Statistics Authority shadow Treasury minister Chris Leslie says the prime minister may be attempting to mislead the public.
The authority said it would look into the issues raised and respond.
National debt is rising. It is expected to fall as a percentage of GDP in 2016/17 under current OBR forecasts.
Mr Leslie wrote to the authority's chairman, Sir Andrew Dilnot.
Labour made a similar complaint last year. Then Sir Andrew wrote back saying all parties in the public debate should understand and distinguish the difference between the national debt and the deficit - the difference between revenue generated and spending each year.
He copied the letter to the prime minister's chief of staff.
