Education secretary Nicky Morgan has said her Labour counterpart Tristram Hunt is "completely wrong" to recommend washing your hair before bed.
The bizarre row kicked off when Hunt was answering questions on website Mumsnet on Monday.
After being complimented on his "fine head of hair", he replied: "Thank you very much for the kind comment!
"Any credit for this must go to Jack – my hairdresser. In terms of tips, I would always recommend washing your hair before you go to bed!"
Morgan faced a similar question from the same user on Mumsnet on Tuesday.
She was told she had a "tremendous head of hair" and was asked for her "top tips for looking unruffled" at Prime Minister's Questions.
Morgan replied: "For once I agree with Tristram in that I have to thank my hairdresser Kate. But he's completely got it wrong on washing your hair before bed!"