A NATO-linked report says the world's largest social-media companies are failing at regulating their platforms to combat the manipulation of information.

Researchers at the NATO Strategic Communication Center of Excellence said in a report released on December 6 that social-media manipulation has become the new front line for antagonists seeking to influence elections, polarize public opinion, and sidetrack legitimate political discussions.

The report comes at a time when British and U.S. officials, among others, are preparing for elections and looking to avoid a repeat of social-media manipulation -- much of which was generated from Russia -- that influenced the outcome of previous votes such as the 2016 U.S. presidential election and the 2016 British referendum of leaving the European Union.

The researchers conducted a four-month experiment during which they purchased social-media engagement on posts across Facebook, Instagram, YouTube, and Twitter, and then followed what happened through the involvement of manipulation service providers (MSPs).

They said the results showed that malicious and inauthentic activity enabled by MSPs often goes unnoticed, which increases the chances that ill-intentioned manipulators are able to interfere in democratic processes.

"Based on this experiment and several other studies we have conducted over the last two years, we assess that Facebook, Instagram, Twitter, and YouTube are still failing to adequately counter inauthentic behavior on their platforms," the study said.

"Self-regulation is not working. The manipulation industry itself is growing year by year. We see no sign that it is becoming substantially more expensive or more difficult to conduct widespread social-media manipulation," it added.

The researchers said they paid a mere 300 euros ($330) to buy more than 3,500 comments, 25,750 likes, 20,000 views and 5,100 followers across the four platforms.

Nearly 19,000 accounts were identified as being used to deliver the interactions purchased.

The NATO StratCom report concludes that new standards and reporting requirements based on "more meaningful criteria" are needed, as well as independent "well-resourced" oversight of social-media platforms.

It also calls for increased transparency on social-media platforms and regulating the market for social-media manipulation.

Though it is accredited by NATO, StratCom is not part of the NATO command structure.