Google has signed its biggest ever Apps for Business deal – signing up Spanish bank BBVA, one of the largest financial institutions in the world.

The company will move 35,000 workers in Spain to Gmail with Google Chat, Calendar, Docs, Groups, Sites and Video and by the end of 2012 the bank expects to have 110,000 workers in 26 countries migrated to the cloud-based platform.

Google says the move will see BBVA’s global intranet become a collaboration portal that all users will have access to. The bank will also create an internal social network to improve communication between workers, it said.

José Olalla, CIO at BBVA said the deal will help workers to remain productive when they are away from the office, helping remote and mobile workers.

"We were looking for a technology that would transform our business operations – not just make our workers more efficient," he said. "Integrating the Google Apps for Business suite with our own tools will allow us to introduce a new way of working where employees have access to all the information they need with just one click, no matter where they are, and can reap the benefits of using advanced collaboration tools."

The contract win is about twice the size of Google’s previous biggest Apps for Business customers – Rentokil Initial and French manufacturing firm Valeo, both of which had around 30,000 users.

The win is a significant one not just for Google but for the cloud computing market in general, as the financial services sector has traditionally been hesitant to move to the cloud due to security fears.

In fact, it was recently announced that the Los Angeles Police Department (LAPD) had abandoned its plan to move the Google Apps because it said the service cannot meet stringent FBI security guidelines.

However Google now says that the BBVA deal shows cloud computing is secure enough for financial services. "Companies of all sizes, including those with tens of thousands of employees, are now embracing cloud computing. It means a lot to us that BBVA, one of the largest financial institutions in the world, has decided to migrate to Google Apps," said Sebastien Marotte, vice president of Google Enterprise EMEA.

"It shows that cloud computing is now a reality – and leading organisations are already realising its potential to transform their business," he added.

Google Apps for Business is competing against Microsoft Office, the traditional enterprise productivity heavyweight. Last year Microsoft launched Office365, an online version of Office.