Prime Minister Gordon Brown "is a man of true grit and determination" who should not be under-estimated, Labour's deputy leader Harriet Harman has said.
She spoke out after shadow foreign secretary William Hague wished her well in her "campaign to be rid of" the PM, saying the country was "sick of him".
Ms Harman said the PM was the right man to take the UK through difficult times.
She said it would not be possible for her to replace him because Britain's men would want to "flee the country".
Ms Harman made the comments at question time, where she was filling in for Mr Brown who is on his way back from the G8 summit in Japan - and follow press reports she might be plotting a leadership bid.
The exchanges came as Mr Hague mocked the prime minister's call for British households to stop wasting food, saying it was time government departments set an example.
Isn't there something supremely ironic about being lectured about food waste by a prime minister who is past his own sell-by date?
William Hague Shadow foreign secretary
Ms Harman agreed, but then made a jibe about Mr Hague's boast when Tory leader about how much he drank as a teenager.
She said that the last person Mr Brown would be taking dietary advice from was someone who thinks a "good diet is 18 pints a day".
Mr Hague hit back, to laughter: "None of that was ever wasted, I can assure you."
He said it was "astonishing", given the prime minister's comments, that expenditure on hospitality in the Treasury, when he was chancellor, "more than trebled".
"Isn't there something supremely ironic about being lectured about food waste by a prime minister who is past his own sell-by date?" he asked.
"Isn't it yet another example of treating people like fools, of preaching prudence but practising profligacy, and waste - isn't this why the whole country is sick of the prime minister?"
He added: "I wish you well in your campaign to be rid of him."
Ms Harman retorted: "You shouldn't under-estimate the prime minister, who is a man of true grit and determination, who will see the country through the difficult circumstances."
She thanked Mr Hague for his "kind comments" about her own leadership chances, but added: "I'm afraid it wouldn't be possible because there aren't enough airports in the country for all the men who would want to flee the country."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.