ABIDJAN, May 26 (Reuters) - A fifth of cocoa purchases by multinational companies in Ivory Coast must be fulfilled by local firms in an effort to improve competition in the world's largest cocoa-exporting economy, according to a government decree on Wednesday.

Until now, major international players have used their greater financial muscle to buy and export all the available cocoa, while local firms lacked access to financing and to European and U.S. chocolate makers to compete on an even playing field.

As a result, around half of local exporters have gone out of business in the past five years, government spokesman Amadou Coulibaly said.

"In order to promote the emergence of national winners in the sector and to create sustainable conditions for their activities, the council (of ministers) has decided to allocate 20% of bean exports to bean exporters and processors," he said.

The decree, whose announcement had been expected in recent weeks, applies also to exports of coffee beans, he said.

The international cocoa companies that currently hold Ivorian export contracts are Cargill, SucDen, Oam , Barry Callebaut, Touton and Ecom.

(Reporting by Ange Aboa Writing by Alessandra Prentice; Editing by Alison Williams and Nick Macfie)