A British government minister sharply criticised Zimbabwean President Robert Mugabe on Tuesday and said it would be premature for Commonwealth leaders to hold out an olive branch to Zimbabwe when they meet later this month.

Zimbabwe withdrew from the Commonwealth, a 54-nation group consisting mainly of Britain and its former colonies, in 2003 after the organisation suspended it following Mugabe's re-election in a poll some observers said was rigged.

The Commonwealth Advisory Bureau, a thinktank, suggested in a briefing paper issued before the October 28-30 Commonwealth summit in Perth, Australia, that the Commonwealth could offer help to Zimbabwe to encourage progress towards democracy.

But David Howell, the Foreign Office minister responsible for Britain's relations with the Commonwealth, said now was not the time for the Commonwealth to make a gesture to Zimbabwe.

No-one is going to encourage, certainly Britain isn't going to encourage, olive branches or anything else to a Mr. Mugabe who is showing no sign of recanting, standing down or removing some of his ZANU thugs from the scene, Howell told Reuters in an interview.

There's got to be big changes inside Zimbabwe, he said.

Most of the change would be led by a regional grouping, the Southern African Development Community (SADC), with South African President Jacob Zuma playing a lead role, said Howell, a member of Britain's upper House of Lords.

But I think the Commonwealth certainly sees itself -- when the time comes, which is not yet -- also being a leading force in helping the recovery of Zimbabwe, the restoration of credible and properly monitored elections and the revival of its whole economy and its role in the world, he said.

SLOW PROGRESS

Mugabe, 87 and in power since 1980, was forced into a unity government with the Movement for Democratic Change after 2008 elections led to mass violence and pushed the resource-rich state into a deeper economic crisis.

The uneasy power-sharing government has brought a measure of economic stability to Zimbabwe which holds the world's second-largest platinum reserves and vast diamond reserves, but diplomats say progress on political reform has been slow.

Mugabe has had a tempestuous relationship with Britain, the former colonial ruler.

Archbishop of Canterbury Rowan Williams, the spiritual leader of 80 million Anglicans worldwide, met Mugabe on Monday to hand him a dossier of abuses against the church and its priests in Zimbabwe.

Howell said there would be a lot of argument at the Commonwealth summit over an experts' report recommending that the Commonwealth act more decisively to uphold human rights among its members, but predicted that positive things would come out of the summit.

Britain and other wealthy Commonwealth nations, such as Australia and Canada, back a stronger focus on rights but some developing nations fear the change could interfere in their affairs.

Howell said there was broad agreement on the need to update the Commonwealth but a healthy debate was needed over how the group could uphold its democratic principles more vigorously.

The worry that this is some sort of new policing regime that is going to get on everybody's backs ... is one that has to be dispelled, because that is not the intention, he said.