Federal regulators are proposing new standards to keep retailers from changing their prices based on individual buyers' data.

The Federal Trade Commission can't outright ban personalized pricing, which is when a retailer customizes the price you pay based on what it knows about you.

But in a letter released Wednesday, the FTC said it planned to hold retailers to existing rules. Personalized pricing may run foul of the FTC Act, "which prohibits unfair or deceptive practices in the marketplace." The collection of personal data to change pricing per-person might also violate the FTC Act's privacy protections.

“When consumers see a listed price, they expect it to be same price that everyone else sees, not the retailer’s estimate of how much they are willing to pay based on their personal data,” said FTC Chairman Andrew Ferguson.

Any personalized pricing that does take place should also be "clear and conspicuous" to the consumer, the letter says, and tell them what data was used to make that personalization.

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Consumer advocates welcomed the clarification. In a statement, Consumer Reports called the move "encouraging," and called for even more clear-cut rules to protect buyers.

"The FTC, Congress, and states should take action to prohibit companies from using consumers’ individual data to personalize prices in the first place," its statement read.

The proposed policy is subject to a 30-day public comment period.