Google accuses Bing of 'copying' its search results
Google has accused Microsoft of cheating, following an investigation known as the 'Bing Sting'.
Google engineers created 100 nonsensical queries such as "hiybbprqag" and inserted a fake result for each.
Within weeks, the same results began to appear on its rival Microsoft's Bing search engine.
Microsoft denies copying Google and accused Google of conducting "spy-novelesque stunts".
Harry Shum, vice president of Bing, said: "We do not copy Google's search results. We use multiple signals and approaches in ranking search results," he added.
"Opt-in programs like the toolbar help us with clickstream data, one of many input signals we and other search engines use to help rank sites," he added.
But Google's Amit Singhal told industry blog SearchEngineLand.com that it was "plain and simply cheating" and he detailed the sting operation in a long blog post.
He said Google decided to conduct its experiment after mis-spelt words and results were replicated on Bing.
"A search for 'hiybbprqug' on Bing returned a page about seating at a theatre in Los Angeles. As far as we know the only connection between the query and result is Google's result page," he said.
"We noticed that URLs from Google search results would later appear in Bing with increasing frequency," he went on.
He concluded that Microsoft was gathering data on what people search for on Google, via either Internet Explorer or the Bing Search toolbar.
"Some Bing results increasingly look like an incomplete, stale version of Google results - a cheap imitation," he said.
Danny Sullivan, a search engine expert, has mixed feelings about what the experiment shows.
"On the one hand you could say it's incredibly clever. Why not mine what people are selecting as the top results on Google as a signal?" he wrote on his blog.
But he also said he had sympathy for Google's view that Bing is doing something wrong.
"Every search engine has its own 'search voice', a unique set of search results that it provides, based on its collection of documents and its own particular method of ranking those.
I think Bing should develop its own search voice without using Google's as a tuning fork," he added.
Wider issues for him include how Google went about setting up its honeypot trap to ensnare Bing and whether it was just a "clever way to distract from current discussions about its search quality".
Google has stressed that it has now removed the one-time code that it added to plant the fake pages.
Had any of its fake queries proved popular, it said that it would have removed the page they linked to.
Mr Sullivan also questioned how much consumers knew about the data capture that allowed Microsoft to gather Google's search results, either via Internet Explorer or the Bing toolbar.
"Do Internet Explorer users know that they might be helping Bing in the way Google alleges? Technically, yes. Explicitly, absolutely not," he said.