The Wall Street Journal quoted James Douglas, head of media at the digital agency Reprise, as saying: "It’s just an amplification of pay-to-play from Facebook."
Last week, Facebook announced its new policy, made in the wake of claims that it was open to publicising fake news stories. The social media company said changes would be made in the algorithm that feeds posts to users in order to increase "meaningful interaction".
"We started making changes in this direction last year, but it will take months for this new focus to make its way through all our products," Facebook chief Mark Zuckerberg said in a blog post.
"The first changes you'll see will be in News Feed, where you can expect to see more from your friends, family and groups."
The WSJ report said marketers were used to such changes as many changes had happened over the years, forcing them to spend more in order to make sure their clients' advertisements were seen by users.
Some ad buyers said this may force them to start looking at other platforms.
Zuckerberg said that one effect of the change would be that people would spend less time on Facebook. "But I also expect the time you do spend on Facebook will be more valuable. And if we do the right thing, I believe that will be good for our community and our business over the long term too," he added.
While Facebook vice-president of product management John Hegeman told Reuters that advertising would not be hit by the change, ad industry workers said they expected ad prices to rise as the number of chances to serve ads declined.
The WSJ quoted Paul Mead, chairman of VCCP Media, a UK-based media agency, as saying: "It’s simple mathematics for a display business: Less time on Facebook and fewer ads can only mean that the ads that do show are more expensive.”