The cash will go on microsites and eCRM programmes to back the launch of its new A-Class, CLS-Class executive saloon, M-Class off-roader and a compact sports tourer (CST) models, which are all set to launch in the next 12 months.
Richard Payne, communications manager for Mercedes-Benz passenger cars in the UK, said the web would help the brand to reach a younger audience, which lies outside its core executive market.
He added: "Our aim over the next 12 months and into the future, is to bring new people to the brand and online is a central part of that - it will assist us in communicating with them."
Work will kick off this month with a microsite for the A-Class, the firm's 'do-anything' vehicle, which has been updated for this year. It is also backing a major email-marketing effort to build a database of sales leads for dealers, who will be invited to take a test drive.
Mercedes is hoping to migrate buyers interested in particular cars to its generic brand email programme in order to cross and upsell other models.
The brand will also sign deals with media owners, such as major online portals and car magazines, to feature content in their online car sections.
Activity will aim to drive traffic to the mercedes-benz.co.uk.
Digital work will be handled by Syzygy, the brand's interactive agency since 2000.
See cover story, p30.