London Lifeboat Week is the RNLI's single biggest fundraising event and runs until March 15.
In previous years, fundraising has concentrated on collections at railway stations and high street locations but this year Proximity has expanded the campaign to include a postal sector-targeted door-drop and supporting radio campaign on LBC, Jazz and Classic FM.
The widening of the campaign is designed to boost awareness of the London Lifeboat Week collections as well as being a source of fundraising themselves.
David Brann, fundraising and communications director of RNLI, said: "We are delighted with Proximity's development of London Lifeboat Week and look forward to a successful fundraising campaign."
London is not the home of the RNLI's traditional supporter despite the capital being home to 150 crew and four of the busiest lifeboats in the country, which research has revealed is not widely known among Londoners.
The research helped developed the core campaign proposition "Show your support for London's unsung heroes". The door-drop creative uses illustrations of the River Thames in London with the outer envelope showing a shot of a rescue throw line, following the shape of the Thames in London, with the copy line "You're our lifeline".
Inside the pack a chart of the Thames in London supports copy providing essential statistics on rescues in the capitaland around the coast, with a case study of a bravery award-winning rescue. Prompts are given for suggested donation amounts, together with examples of what these could buy for RNLI in terms of equipment.
The 30-second radio commercial features former newsreader Michael Buerk, who presents BBC One's '999' programme, with a script highlighting RNLI's activity on the river.
Elly Woolston, deputy chairman of Proximity, said: "The RNLI is a vital but undervalued resource in London. We hope our campaign will bring it the support it deserves."
Proximity won the direct marketing account for the Royal National Lifeboat Institution two years ago after pitching against WWAV Rapp Collins and 141.
The London RNLI campaign follows a revamp of its communications material and a complete brand redesign by the Design Group. The RNLI and the lifeboat service wanted to bring the same fresh new look to its recruitment literature and advertising.
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