Although still in the testing phase, the firm says it is the "first step in improving the speed, accuracy and comprehensiveness of search results".

The new engine will replace Google's current one after tests are complete. Martin McNulty of search marketing specialist Trafficbroker said the upgrade threatened to put Microsoft's new engine, Bing, "in the shade".

"Google have let Caffeine quietly slip out. It talked about vertical specific searches while quietly doubling the speed and starts introducing real-time results and news feeds," he said. "Bing was launched with a massive media budget. Trouble is, Bing presents itself as an alternative to something that users are still - for now - happy with," he added.