Octopus has been hired to target ‘hard-to-reach' groups including ethnic minorities and the disabled.
It will also aim to prepare Business Link customers for the outsourcing of the service next April, when Serco will become its national operator.
Serco was selected to take control of Business Link last year after a tender by the Department for Trade and Industry.
Business Link can give information and other help to businesses with up to 259 staff – in the London area, around 110,000 firms.
Under TUPE legislation, Business Link staff will move across to Serco.
To avoid any agency complications concerning the new legislation, Octopus's contract has been timed to end at the handover.