LONDON — In a broad legal rationale for collecting information from Internet use by its citizens, the British government has asserted the right to intercept communications that go through services like Facebook, Google and Twitter that are based in the United States or other foreign nations, even if they are between people in Britain.

The British position is described in a report released Tuesday by Privacy International and other advocacy groups. The report, confirming a summary seen Monday by The New York Times, says the findings are based on a government document that the groups obtained through a lawsuit.

The government document, released with the report, says contact between people in Britain through social networks based elsewhere, or use of search engines located outside Britain, constitutes “external communication,” and as such, is subject to interception, even when no wrongdoing is suspected.

By contrast, under British law, “internal communication” between people based in the country may be intercepted only when there is suspicion of illegal activity as specified in a government-issued warrant overseen by the courts.