The Conservatives have called for the Commonwealth to set up a "powerhouse group" of influential members to restore its credibility after its failure to address the crisis in Zimbabwe.

Michael Ancram, the shadow foreign secretary, said the organisation would enjoy more influence if it appointed an inner core of up to eight members to act as its representative.

"Since its inception, the Commonwealth has adapted to changing circumstances through its rolling declarations of principles.

"At the same time its international importance has declined. Today the Commonwealth generates more affection than awe. And that is not enough," said Ancram.