The London Borough of Hillingdon is to migrate to Google Apps for Enterprises in February 2012 in a move it said will save it £3m over four years.
The council will migrate 3,500 staff from Microsoft Outlook to Google Apps.
The migration will take two years and see staff moved onto web-based email and calendar within four or five months, with these services to be supplemented by instant messaging and videoconferencing at a later date.
Steve Palmer, head of ICT at Hillingdon, said the council would save money and be more productive following the move.
"The council will save £3m because it won't have to pay for licences, there is less of an investment in infrastructure, too, as the migration reduces the need for local storage and server space for data. We'll also need less support from our in-house IT team," he said.
"In terms of productivity, Google Apps allows us to collaborate internally and access documents at any time using instant messaging and videoconferences, this will then help us to find new ways of being able to deliver public services," he said.
He added that many staff use Google Apps in their private lives, which should help to make the move relatively painless. For those not familiar with the service, there will be a structured training programme, Palmer added.
Palmer said that although other councils are looking into moving to the cloud Hillingdon is the first to do so.