BRUSSELS (Reuters) - Tech giants will have to do more to weed out illegal and harmful content while online gatekeepers will be bound by a list of dos and don’ts under new rules aimed at reining in their power, Europe’s antitrust chief said on Thursday. European Competition Commissioner Margrethe Vestager also proposed new powers for enforcers to tackle market failures in digital markets and to stop new ones from emerging. Under the proposed Digital Services Act, online platforms will have to check sellers’ identities before they can use their services in a move aimed at countering illegal and dangerous content. The tech companies will have to produce reports on their actions and inform users who pays for the advertisements that they see and why they have been targeted by certain adverts, Vestager said. The second set of rules called the Digital Markets Act is targeted at online gatekeepers. “That proposal will have two pillars,” Vestager told a European Policy Center event. “The first of those pillars will be a clear list of dos and don’ts for big digital gatekeepers, based on our experience with the sorts of behaviour that can stop markets working well.” Practices not allowed include pushing one’s own services, known as unfair self-preferencing, making it difficult for users to switch platforms or to use more than one service. Vestager said the second pillar of the Digital Markets Act was to set up a harmonised market investigation framework across the 27-country bloc. “That would give us a harmonised set of rules that would allow us to investigate certain structural problems in digital markets and, if necessary, we could take action to make these markets contestable and competitive,” she said. Vestager will announce the new draft rules on Dec. 2. She will need to reconcile her proposal with those from EU countries and the European Parliament before it can become legislation.