The station is hoping to build the reach of breakfast DJ Neil Fox, whom it recruited last September, with "March Money Madness" running every weekday throughout the month.
In his debut Rajars, the former Capital FM DJ attracted 682,000 listeners, up 5.7% on the previous quarter, but flat year-on-year.
The campaign broke on Monday with cross-track posters on the Tube, with a follow-up burst on Greater London bus supersides. Creative is by St Luke's and media planning and buying by Starcom.
The Daily Mail will also support the promotion in return for on-air mentions. Starcom plans and buys media for the Daily Mail as well as other Associated Newspapers titles.
Steve Parker, UK buying director for Starcom, said: "The partnership with the Daily Mail is a strong fit and will add real energy and scale to the whole promotion."
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