Manhattan State Senator Liz Krueger today laid out a novel strategy to undermine opposition to new restrictions on firearms—having gun control supporters join the pro-gun National Rifle Association and act as a Trojan horse.

Ms. Krueger, one of the state’s leading progressive Democrats, called for the creation of the covert cell within the NRA—the nation’s largest pro-firearms lobby—at a pro-gun control event at Hunter College. One of the advocates at the event suggested sitting down with leaders of the NRA to try to identify areas for consensus and compromise, a recommendation Ms. Krueger took a step further.

“I might propose another cultural approach: all of us who actually care about gun violence might want to join the NRA, and create our own forum within the NRA to say ‘we don’t agree with their current policy,’ ” she said.

The Upper East Side state senator argued that gun control advocates might even be able to gain a numerical advantage within the group.

“I actually think we outnumber them, by the way. And if, maybe if we all join, and created our own platform, we could switch the dialogue, even within an organization who I think has done so much harm,” she said.

Ms. Krueger is an aggressive supporter of New York’s SAFE Act, a 2013 package of regulations on assault weapons and ammunition passed in the wake of the Sandy Hook Elementary School massacre and widely touted as the strongest gun control legislation in the nation. But she argued that federal regulation is necessary to prevent guns from entering New York from states with looser laws.

Joining the NRA requires $25 donation for a single year, and entitles the new member to a free heavy-duty duffel bag and a subscription to their choice of one of the group’s three magazine publications. However, one must be a dues-paying member of the organization for five years in order to have voting power—or have signed up for the $1,000 lifetime membership.

The group did not immediately respond to requests for comment.