In a bizarre throwback to the days of playground 'your mum' jokes, the Prime Minister quipped: "I think I know what my mother would say. She'd say: 'Put on a proper suit, do you your tie and sing the national anthem.'"
But it seems the Conservative leader could do with heeding his own sartorial advice a little more.
He's quite happily had meetings with world leaders, posed for national election campaign posters and wondered round the country meeting constituents, all the while without wearing either a suit or tie.
Disgraceful behaviour, we're sure Mary Cameron would agree.
So here are 9 times the Prime Minister could have done with paying more attention to his mother's apparel advice.
1. Prepping for the G8 with Putin
2. And later, sharing a laugh with Angela Merkel
3. Posing for his 2010 election poster
4. Skyping with Obama
5. Slipping-out at the Lord Chancellor's banquet
6. Speaking at a general election rally
7. Today, talking sans-tie in London - with Philip Hammond and Greg Hands both sporting ones
8.Campaigning for tie-wearing Zac Goldsmith
9. He managed it here. But did the PM dare admonish his chief election strategist, Lynton Crosby, for turning up to work like THIS?!
We doubt it.