Microsoft has unveiled online versions of several key Office products, including Exchange, SharePoint, Office Live Meeting and Office Communications, enabling UK businesses to subscribe on a monthly basis rather than having to pay upfront to purchase and install the software locally.

Collectively called Business Productivity Online Suite (BPOS), the services are available for UK companies to test from today, with commercial availability coming in April. After this date, customers signing up will be allowed a free 30-day trial before payments kick in.

UK BPOS marketing manager Gill Le Fevre said that the four services - Exchange Online, SharePoint Online, Office Live Meeting and Office Communications Online - can be purchased as a suite or individually.

"Our software and services strategy lets customers decide how they want to invest in IT, whether they want to operate servers themselves or let Microsoft host services such as Exchange and let us take care of all updates and patches, " she said.

BPOS also allows customers to pay only for the capacity they need, and scale up as and when necessary, Le Fevre added.

The online products have essentially the same functionality as the installed versions, according to Microsoft, and the whole suite costs from £10.04 per user per month.

With Exchange Online, customers get a minimum 5GB of shared storage for email, calendar entries, shared tasks and contacts. Users can access their inbox via Outlook from a PC, Outlook Anywhere or Outlook Web Access. This is priced from £6.69 per user per month.

A 'Deskless Worker' option for Exchange Online provides browser-based access only, at a reduced price of £1.34 per month. This option is aimed at workers who do not necessarily use a PC, but still need occasional access to email, according to Le Fevre.

Similarly, SharePoint Online offers collaboration and document storage capabilities for £4.85 per month, while a Deskless Worker option gives read-only access for a lower tariff of £1.34 per month.

Both Exchange Online and SharePoint Online can be expanded with additional storage for £1.67 per gigabyte per month.

Office Live Meeting offers web client support for videoconferencing for £3.01 per month, while Office Communications Online offers instant messaging and presence support for £1.67 per month. However, unlike the standard PC Office Communicator client, this does not yet feature the ability to make voice-over-IP calls, although Microsoft pledged that this will come at a later date.

One customer that has already been trialling BPOS is The Wise Group, which is planning to deliver Exchange and SharePoint access to 500 employees over the next few months using a mixture of PCs and thin client terminals.

Wise Group chief information officer Alan Lee-Bourke said that using Microsoft's online services will save the organisation at least 10 per cent against the cost of installing and operating the same applications internally.

"It also leaves us free to concentrate on data management rather than on managing boxes. It is too compelling to be ignored," he added.

Some businesses may be wary about Microsoft hosting key applications for them, however, especially in light of last week's prominent failure of Google's Gmail service.

Le Fevre claimed that Microsoft can deliver "99.9 per cent availability", and that the firm will refund customers their subscription fees for the month if the service level should drop below 95 per cent during that period.

She also said that UK customer data will be stored only in Microsoft datacentres located within the EU, and that customers will have their data returned to them if they decide to terminate the arrangement.

Microsoft has already stated that browser-based versions of other Office applications, namely Word, Excel, PowerPoint and OneNote, will be supported with the next version of Office, now set to ship in 2010. Currently codenamed Office 14, an alpha release build of this suite was distributed to selected testers in January.