Ed Miliband has been accused of being out of touch after under-estimating the cost of his family's weekly food shop.
The Labour leader said the supermarket bill came to around £70 or £80 but later insisted that he was referring only to the amount spent on " basic" groceries such as fruit and vegetables.
Critics were quick to seize on the comments as proof he did not know the details of his household bills and instead "took a punt".
Mr Miliband made the initial estimate after being pressed about his food spending when he was talking about Labour's plans to tackle t he cost-of-living crisis on ITV's Good Morning Britain.
He said: "We probably spend £70, £80 a week on groceries at least, probably more than that. The point is that different families will have different costs that they face but what I am clear about is that there is a crisis facing so many people."
The Labour leader was told on the programme that the average weekly bill for a family of four is more than £100 - so he would be spending "significantly more" than £70 to £80.
"Lots of people are facing a real struggle," he replied. "I am relatively comfortably off, but what I know is that there are deep issues that need to be tackled and we are determined to tackle them."
He later admitted that his shopping estimate may have been on the low side, saying he had been thinking of the bill for "basic groceries".
"Well, I said this morning it was on the basic groceries, the basic fruit and vegetables, about £70 or £80 - the total shopping bill was slightly higher than that, obviously," he told BBC Radio Oxford.
"On the basics, I was saying it was about £70 or £80 but the overall shopping bill would obviously be higher."
Figures from the Department for Environment, Food and Rural Affairs (Defra) Family Food survey show the average weekly expenditure on all household food and drinks in 2012 was £29.29 per person, an increase of 4.6% on 2011.
Total expenditure on household food and non-alcoholic drink rose by 4.3% to £25.98 per person and was 8.9% higher than in 2009.
Figures from the Office for National Statistics (ONS) showed the average weekly expenditure for a household with two adults and two children on food and non-alcoholic drinks in 2012 in the UK was £83.60.
The Labour leader's comments sparked robust exchanges on the Mumsnet website, which racked up more than 100 posts on the issue.
TheWordFactory wrote: " Basically, he doesn't know! He took a punt and made himself look daft. I suspect he hasn't stepped a foot in Tesco since 1982."
Contributor bleedingheart wrote: " It is so ridiculous to try and perpetuate this 'man of the people' nonsense.
" Of course politicians need to be aware of the struggles people face and work on the solutions but I don't for a second think Milliband does his own shopping or Cameron for that matter."
LostMyPants wrote: " I'm no fan of Ed, but it could easily be true. Just because you're rich it doesn't mean you have to waste more food."
Shedding wrote: " I think they could easily spend that little in groceries due to eating out of the house so often? Breakfast meeting, lunch on the run, might just appear on the desk, school dinners for the kids, dinner laid on at some kind of event?"
A Tory source said: "It's the same old economic incompetence from the Labour Party that gave Britain the biggest peacetime deficit in history.
"They have no long-term plan to fix the economy and Ed Miliband can't even get the numbers right for his political gimmicks."
Nadine Dorries, Conservative MP for Mid Bedfordshire, said: "If Ed Miliband said his family weekly grocery shop cost £80, he was making it up on the hoof and digging himself a hole - which pretty much speaks for this leadership of the Labour Party."
Priti Patel, Conservative MP for Witham, told The Telegraph: "It sums him up for the hypocrite he is. Out of touch with hard-working Britain."