Bell Pottinger was hired last week after a three-month pitch process, in which eight agencies were finally whittled down to a shortlist of three.
Vauxhall manager of business affairs David Crundwell said Bell Pottinger would work with his in-house communications team of 15 on a 'range of projects within our overall PR and marcoms brief'.
Bell Pottinger chairman Kevin Murray said that a 'flexible' team - drawing various resources of the agency's parent company, Chime Communications - would be used to work on the Vauxhall account.
The bulk of Bell Pottinger's work will be to boost the profile of the company, its vehicles and its presence at the forthcoming British International Motor Show.
The event - at which the Meriva marque will be unveiled - will be held at Birmingham's NEC from 23 October to 3 November.
Bell Pottinger will also launch and handle PR for Vauxhall's centenary next year, but neither Crundwell nor Murray would reveal details of Vauxhall's PR plans for this.
Recent Vauxhall ad campaigns have focused on themes such as fun and innovation.
The strapline on the latest ads for the Corsa model is 'Put the fun back into driving', and ads for the Vectra promise 'New Vectra - New Rules'.
It is likely upcoming PR campaigns will seek to re-inforce these messages.
Hill & Knowlton and GPC International formerly handled the consumer and lobbying work respectively for Vauxhall. The company has already ceased working with these agencies.
In March this year the final car rolled off the production line at the firm's factory in Luton, Bedfordshire, with the loss of 1,900 jobs.
Vauxhall retains factories in Luton and Cheshire. The former produces Vivaro vans and 4x4 Fronteras while the latter produces Astras, Vectras and V6 engines.