A Treasury minister has been accused of not knowing "the basic facts of her job" after struggling to answer questions about the rise in national debt.
Labour said it was "terrifying" that Laura Trott is in charge of the country's finances after she was challenged for repeatedly claiming that debt is falling as a proportion of GDP.
Ms Trott said she had "different figures" when she was presented with the latest official projections from the Office for Budget Responsibility (OBR), which suggest an increase in debt over the next five years.
According to the fiscal watchdog's November outlook, debt is forecast to climb as a percentage of national income from 89% in 2023/24 to 92.8% in 2028/29.
Appearing on BBC Radio 4's PM programme, Ms Trott was asked how the government can afford potential tax cuts ahead of the next election, given that one of Rishi Sunak's five key pledges is to reduce national debt.
She said: "The central pledge... is that debt needs to be falling over the five-year fiscal forecast as a percentage of GDP, which it is."
Presenter Evan Davis, a former economist, interjected, telling her the debt is set to be "higher in five years than now" and pointing to the latest projections.
She maintained debt is falling as a percentage of GDP, but when challenged again, Ms Trott appeared to start saying "I'm not sure", to which Davis replied: "This is really basic... I'm amazed that you don't know that debt is rising."
The minister said: "I think I need to have the figures. I've got different figures which... I think we just need to... yeah." She did not specify which figures she meant.
Labour said it was "terrifying" that people unaware of "the basic facts" are in charge of the country's finances.
Ms Trott's opposite number, Darren Jones, said: "The Tories have crashed the economy and doubled the national debt over the last decade. This evening we discover that Laura Trott, Jeremy Hunt's number two, doesn't even know the basic facts of her job.
"It's terrifying to think these people are not just in charge of the country's finances, but still think they can lecture anyone else."
The government has previously been chastised for claiming that debt is falling.
In December, the head of the statistics watchdog said the assertion, made by Mr Sunak two times in November, may have caused "confusion" and "undermined trust in the government's use of statistics".
The OBR forecast which Mr Davis was citing says that debt will start to fall in the latter half of this decade - but it will still be higher in five years time than it is now.
The projection is that debt will rise from 89% of GDP now to 93.2% in 2026-27. It will then decline in the final two years to 92.8% of GDP by 2028-29.
Downing Street pointed to this when contacted for comment, saying that means the government "is on track to meet our commitment to have debt falling in five years' time".