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The Federal Communications Commission shouldn't vote on whether to end net neutrality just yet, a group of 28 senators said in a letter sent Monday. It needs to first investigate claims that hundreds of thousands -- and perhaps millions -- of public comments on the controversial policy change appear to have been made by bots posing as regular people, they wrote.

"Without additional information about the alleged anomalies surrounding the public record, the FCC cannot conduct a thorough and fair evaluation of the public's views on this topic," the senators, lead by New Hampshire Senator Maggie Hassan, wrote.

The FCC, under the leadership of Chairman Ajit Pai, is scheduled to vote Dec. 14 on a policy that would roll back regulations on internet service providers. Opponents say the rollback will make it legal for internet providers give preferential treatment to some web services over others, making it harder for users to access everything the internet has to offer with the same quality of internet connection.

In response to the letter, an FCC spokesman said in an email, "The vote will proceed as scheduled on December 14."

The fake comments first came to light in May, when the public comment period was still open. Last week, the Pew Research Center estimated that more than half of the online comments came from duplicate or temporary email addresses, a sign that they were part of a campaign to spam the FCC.

New York Attorney General Eric Schneiderman has also called on the FCC to investigate the allegedly fraudulent comments. In an open letter, he said his office estimates that public comments came from fakes posing as "hundreds of thousands" of Americans. This violates New York law, Schneiderman said, so he is investigating the issue on behalf of New Yorkers.

In their letter Monday, the senators said the FCC needs to get a better picture of the public record, "as understanding that record is essential to reaching a defensible resolution to this proceeding."