Speaking at the unveiling of a scheme to reduce the amount thrown away, Mrs Birtwhistle, 61, pointed out that seven million tons of produce ends up in the bin each year. "We have become a throwaway society, food being just one of those things," she said.
"With washing machines, it's now cheaper to buy a new one than it is to get one repaired - and food is all part of that culture. There is huge environmental cost that generations after us are probably going to have to pay for. It's about being responsible."
Mrs Birtwhistle, who won last year's Bake Off after impressing viewers with her no-nonsense approach, prides herself on never throwing away food.
She suggested that cooking multiple meals leads to more waste because it generates more leftovers, which simply don't get eaten.
How would she handle a family full of demanding fussy eaters? "If I had teenagers now I'd give them a role - we would have a rota to say you're on fridge duty," she said.
"I'd say, by the time we go for our next shop, the fridge needs to be empty. So instead of getting to shopping day and everything in there goes in the bin, we've used everything up."
Mrs Birtwhistle said she understood the temptation for parents to simply cater to individual preferences, but insisted that eating together is important.
"When you've got a family to feed there is a tendency to fill a fridge with stuff," she said.
"[But] I'm a big believer in sitting down as a family to a meal rather than everybody just having whatever they fancy at any time."
- Daily Mail