The promotion is to mark Lamb’s announcement that it will be supporting the Royal National Lifeboat Institution during 2010.
It will appear on around 100,000 bottles and brand owner Halewood International will be donating £1 to the charity for each of the first 25,000 competition entries it receives.
The competition prize is a 14-night cruise for two with Fred Olsen Cruises.
Senior brand manager Sue Beck said: “This is the first time that Lamb’s has supported a charity in this way.
“The RNLI provides a perfect fit for the brand due to Lamb’s longstanding synergy with the sea.”