The loss of the high-profile account will come as a blow to the incumbent agency MediaVest Manchester, but the creative account remains with the Dorset agency Blair Fowles Advertising.
Land of Leather spends the bulk of its advertising budget on press, although there have also been television and cinema campaigns.
Most recently it ran a TV campaign featuring Frank Bruno dressed up as a doctor with the strapline: "Crack up this Easter."
Land of Leather is based in Northfleet in Kent, and its first store opened in Croydon in 1993. It has embarked on an expansion programme, and from 1997 has grown from having three stores to 40 retail outlets and four warehouse operations.
In the past financial year it more than doubled its annual sales turnover to £71.9 million, although pre-tax profits were fractionally down because of the expansion of the number of stores in Scotland and the north of England.
Land of Leather has ambitions to expand its number of stores to about 120 and is focusing on large out-of-town units rather than small stores.
Christine Walker, the founding partner of Walker Media, said: "Land Of Leather is in a new stage of development and we look forward to making a major contribution to its future success."
Peter Ling, Land of Leather's marketing director, added: "Our media spend has increased significantly as we've grown our retail presence in out-of-town parks across the country and been the beneficiary of increased customer patronage."