Fraud, scams, and "unfair" terms and conditions all need to be cleaned up on Facebook, Twitter, and Google+, the European Commission has said—warning the US firms that any failure to comply with the order will lead to sanctions.

It comes after the trio of free content ad networks were put on notice in November last year, when Brussels' officials asked the companies to address two areas of concern.

Facebook, Twitter, and Google—all of which are routinely blasted by regulators and lawmakers in Europe—have one month to submit proposals for how they plan to comply with the EU's demands. If their offers come up short against the bloc's regulatory framework, then consumer authorities could threaten to take enforcement action, the commission said.

"Given the growing importance of online social networks it is time to make sure that our strong EU rules, that are there to protect consumers from unfair practices, are complied with in this sector," said Brussels' justice commissioner, Vera Jourová.

"It is not acceptable that EU consumers can only call on a court in California to resolve a dispute. Nor can we accept that users are deprived of their right to withdraw from an online purchase. Social media companies also need to take more responsibility in addressing scams and fraud happening on their platforms."

The commission—citing the Unfair Contract Terms Directive—wants the companies' terms of service to "be brought into conformity with European consumer law." It said:

Social media networks cannot deprive consumers of their right to go to court in their Member State of residence;

Social media networks cannot require consumers to waive mandatory rights, such as their right to withdraw from an on-line purchase;

Terms of services cannot limit or totally exclude the liability of Social media networks in connection with the performance of the service;

Sponsored content cannot be hidden, but should be identifiable as such;

Social media networks cannot unilaterally change terms and conditions without clearly informing consumers about the justification and without given them the possibility to cancel the contract, with adequate notice;

Terms of services cannot confer unlimited and discretionary power to social media operators on the removal of content;

Termination of a contract by the social media operator should be governed by clear rules and not decided unilaterally without a reason.

It has also called for a crackdown on fraud and scams on the networks. The commission said the firms should remove any such content once they become aware of it on their sites.

Twitter declined to comment. Google and Facebook hadn't immediately got back to Ars with a statement at time of publication.