The service, NatWest One, lets users combine loans, overdrafts and savings into the same account to reduce the rate of interest. The campaign will also push the fact that savings in the account will not be liable to tax.
Created by web agency Zentropy Partners and booked by Media.Com, the ads will run on the PDA versions of Times Online and Guardian Unlimited.
Supporting offline press, billboard and railway concourse activity, the digital drive will use skyscrapers, expandable banners and Overlayz on sites including ThisIsLondon, asserta home and moneysupermarket.
com, while a microsite will run on MSN UK.
NatWest also plans to send 250,000 promotional emails with details of its own microsite (www.natwest.com/one).
Ron Kalifa, head of internet banking at NatWest, said the activity would raise awareness of the bank's profile as a mortgage provider. He added: "This campaign has included a number of NatWest firsts, such as a roadblock of the Times Online site and promotion to PDAs."