The new partnership between the two companies involves the marketing and management of new and existing cards.
All new and existing cards will continue to be branded Alliance & Leicester (A&L), the company said.
But customer service functions and administration and will transfer to MBNA, with MBNA becoming the credit card provider.
Cost saving
There are currently 1.3 million A&L cards in circulation in the UK.
The bank said that it had taken the decision to sell the accounts, because the credit card market was becoming increasingly global - and it did not have the "scale" to compete with these companies.
MBNA is one of the the world's largest credit card companies.
A&L said the decision was also part of its strategy to focus on four "core" products areas: Current accounts, personal loans, savings and mortgages.
Other partnerships
The bank recently announced an extension of its partnership with Legal & General to sell life assurance products.
In May 2001 it began selling the life assurer's long-term savings products.