A Calgary charity says it's "pathetic" that people would steal from veterans after at least 21 poppy donation boxes were stolen from stores across the city.

The most recent theft took place on Monday, according to Calgary police.

David Howard is the head of the Canadian Legacy Project. (Kate Adach/CBC)

"They're stealing from soldiers [who] actually gave them the freedoms they have to be wandering the streets," said David Howard of the Canadian Legacy Project.

"So it's a pathetic thing for it to happen," he added.

Howard says poppy boxes often collect about $50 each — funds that are desperately needed this year because donations are down 11 per cent.

"It's a tough economic climate in Calgary [so] every dollar counts," Howard said.

"Those dollars are used to support our vets and those in need, and for the veterans' food drive ... that's a lot of money."

Police say they're working with retailers to make sure they don't keep a lot of money in the boxes.

They say the theft of poppy donations is often a crime of opportunity and desperation.