DENVER — Colorado officials have cleared the language of a proposed ballot measure that would establish the nation’s first legal limits on buying smartphones for children.

Backers of the move to forbid the sale of smartphones to children younger than 13 would now need about 300,000 voter signatures for the proposal to make the 2018 ballot.

The ban would require retailers to ask customers about the age of the primary user and submit monthly reports to the state on adhering to the requirement. Retailers who sell a phone for use by a youngster could be fined $500.

The campaign is being led by Denver-area father and doctor Tim Farnum.

“Eventually kids are going to get phones and join the world ... but little children, there’s just no good that comes from that,” he told The Coloradoan.

Farnum said he was inspired to make the push after watching his own kids struggle with the psychological effects of always having a device in hand.

Democratic state Sen. John Kefalas said he understands the reasoning behind the proposed law. But he told the newspaper that it would overstep the government’s role.