People caught with more than 100 marijuana plants, a number Greater Toronto "grow houses" usually exceed, should get an automatic 14 years in prison, Scarborough-Agincourt MP Jim Karygiannis says.

Though he was part of a Liberal government that said it would decriminalize small amounts of marijuana, Karygiannis said he's now proposing harsher sentences for cultivating pot because "something has to be done" to combat grow operations.

It's an approach that's been criticized in the U.S., where mandatory minimum sentences have swelled prison populations for decades, but the MP said grow houses that bring crime into neighbourhoods and make houses "unfit to live in" have "reached epidemic proportions" in his riding, with more than 70 busts in 2004 alone.

"When you put a grow house next to my house, you put me and my family at risk," he said, since illegal connections to the electrical grid have caused fires.

"I've seen houses that were burned. I've had a few burned in my area."

The MP's motion, which was submitted last week but isn't yet scheduled for debate in the House of Commons, said people caught growing three to 20 marijuana plants should do a mandatory two years in jail.

For 21 to 49 plants they should get a mandatory five years, seven years for 50 to 100 plants and 14 years in jail for more than 100 plants, the motion says.

All but one of the 39 grow houses busted in the GTA last month after a joint forces police investigation allegedly had more than 100 plants inside.

Such mandatory sentencing is not good policy and has never worked, Alan Young, an Osgoode Hall Law School professor and advocate for legalization said in an interview this month.

"It has not much deterrent impact but it definitely will fill prisons," he said. "People generally don't take the severity of punishment into account in planning their illegal activities."

Before its defeat, the Liberals had introduced legislation, Bill C-17, that would have decriminalized the growing of one to three plants (which can now bring a sentence of up to seven years) and substituted a $500 fine.

Proposed sentences for those with four or more plants under the bill were up to five years, up to 10 years for 26-50 plants and up to 14 years for more than 50 plants.

These days, conditional sentences are still being handed out to people found in smaller grow operations, though those with the larger ones tend to get six to 15 months or more than three years for "very sophisticated" operations, Young said.

Karygiannis said light sentences are a "revolving door" for grow house operators that must stop, but asked if he thought minimum sentences have worked in the U.S. or would prevent grow houses here, the MP responded that "something has to be done. This is what my community has asked me to do."

Politicians from other levels of government have made grow houses one of their top issues in Agincourt. A multi-level Marijuana Task Force has stepped up communication between governments and agencies, resulting in some progress, Karygiannis said.

"The criminals know we're not going away."

Recently, five people were charged in the 2005 murder of Pei Ding Xu, which police have alleged was connected to a conflict between rival gangs over Scarborough grow houses.