A panel of EU data protection watchdogs said the move was necessary to prevent the law from being circumvented.
Google currently de-lists results that appear in the European versions of its search engines, but not the international one.
The panel said it would advise member states' data protection agencies of its view in new guidelines.
At present, visitors are diverted to localised editions of the US company's search tool - such as Google.co.uk and Google.fr - when they initially try to visit the Google.com site.
However, a link is provided at the bottom right-hand corner of the screen offering an option to switch to the international .com version. This link does not appear if the users attempted to go to a regional version in the first place.
Even so, it means it is possible for people in Europe to easily opt out of the censored lists.
Google An option to switch to Google.com is available to those who do not want to use its regional search tools
The data watchdogs said this "cannot be considered a sufficient means to guarantee the rights" of citizens living in the union's 28 member countries.
A spokesman for Google said: "We haven't yet seen the Article 29 Working Party's guidelines, but we will study them carefully when they're published."
The right to be forgotten was established in May by a ruling from the Court of Justice of the European Union.
It said a Spaniard had the right to stop an article referring to his financial troubles appearing in Google's results, bearing in mind the event had happened 16 years before and he had put his troubles behind him. The decision did not affect the article actual presence on the net.
The court added that judgements about other complaints would need to balance "sensitivity for the data subject's private life [against] the interest of the public in having that information".
The European Commission later clarified that search engines would have to delete information if they had received a request from the person affected by the result and had judged that it met the court's criteria for deletion. In cases where search engines decide not to remove the links, the person involved can take the matter to their local data watchdog or the courts.
Google logo Google has resisted previous calls to extend the right to be forgottenSince then, Google has received more than 174,000 requests concerning more than 602,000 links.
The company says it has removed 41.5% of the links it has weighed up, and left 58.5% of them as they were.
Examples include the Google's removal of a webpage about a murder that mentioned the name of the victim's widow, and its refusal to delete links to recent articles about a man's arrest for financial crimes that he wanted deleted.
The US tech giant has previously defended its interpretation of the law, saying less than 5% of Europe-based users opted to switch to Google.com, and that most of those who did were travellers abroad.
"Europe is much more concerned than the US about issues of privacy, particularly the Germans," commented Daniel Knapp, director of advertising research at the consultancy IHS.
"But what has come about as a result is a regional approach to a global problem. It has put a huge administrative burden on Google to verify the right-to be-forgotten claims, and it doesn't really want to take on that role.
"So, resisting the right to be forgotten on a global scale is also a tactic for it to exert pressure on the European Commission to revisit this right and to highlight that it isn't practically feasible."