A group of Democratic U.S. lawmakers on Tuesday urged Facebook Inc (FB.O) to drop plans for a version of photo-sharing app Instagram for children younger than 13, saying the social media company had failed to “make meaningful commitments to protecting kids online.”

Senators Ed Markey and Richard Blumenthal and Representatives Kathy Castor and Lori Trahan said Facebook had not addressed their concerns. Facebook told the lawmakers in an April 26 letter made public on Tuesday that it does not have a set timeline for the version, but expects development will "take many months."

“Facebook has a clear record of failing to protect children on its platforms," the lawmakers said in a joint statement. "When it comes to putting people before profits, Facebook has forfeited the benefit of the doubt, and we strongly urge Facebook to abandon its plans to launch a version of Instagram for kids."

Last week, a group of 40 state attorneys general also urged Facebook Chief Executive Mark Zuckerberg to abandon those plans.

A Facebook spokesman said Tuesday "as every parent knows, kids are already online. We want to improve this situation by delivering experiences that give parents visibility and control over what their kids are doing."