Twitter has clashed publicly with Google over changes to the dominant web search engine that promote Google+, its own social network.
Announced on Tuesday, Google's “Your World” update means users will see more links to Google+ when they search the web, including in part of the results page usually set aside for advertising.
It is the latest example of Google promoting its secondary services via search, a practice currently under investigation by European competition authorities for alleged monopoly abuses.
“You can find relevant Google+ posts from friends talking about an amazing trip they just took, whether they’ve shared privately with you or publicly,” Google said in a blog post.
"Starting today, if you search for a topic like [music] or [baseball], you might see prominent people who frequently discuss this topic on Google+ appearing on the right-hand side of the results page."
The move angered Twitter. Its most senior lawyer, Alex Macgillivray, branded Tuesday a “bad day for the internet” and accused Google of “warping” search.
Twitter followed his comments with an official statement complaining that “Your World” would make it harder for web users to find relevant tweets.
“For years, people have relied on Google to deliver the most relevant results anytime they wanted to find something on the Internet,” it said.
“Often, they want to know more about world events and breaking news. Twitter has emerged as a vital source of this real-time information, with more than 100 million users sending 250 million Tweets every day on virtually every topic. As we've seen time and time again, news breaks first on Twitter; as a result, Twitter accounts and Tweets are often the most relevant results.
“We're concerned that as a result of Google's changes, finding this information will be much harder for everyone. We think that's bad for people, publishers, news organizations and Twitter users.”
Google responded via Google+, entering into an extraordinary public argument with Twitter.
It said it was “a bit surprised by Twitter’s comments about search plus Your World, because they chose not to renew their agreement with us last summer”.
The retaliation referred to Twitter’s refusal to allow Google to fully index tweets because it would agree to its terms. In October, its chief executive, Dick Costolo, told The Telegraph “we just can’t agree on what the appropriate value exchange is”.
Twitter does have a deal with Microsoft to allow Bing, Google’s biggest search engine rival, to index tweets.