By Adrian Croft

LONDON (Reuters) - Prime Minister Gordon Brown said he would lobby for support for his plan to make banks pay for any future bailout at a Commonwealth summit this week.

He also wants Commonwealth leaders meeting in Trinidad and Tobago from Friday to give a push to climate change negotiations and to send a signal that Zimbabwe could be re-admitted to the 53-nation organization if it goes through with reforms.

Brown, whose government spent billions bailing out British banks, pressed the Group of 20 major economies this month to come up with a plan to make banks pay for any future rescues.

One option Brown mentioned, a global financial transactions tax, was immediately shot down by the United States.

Brown indicated he was not discouraged by the initially cool reception given to his proposal and would continue to push it at the Commonwealth meeting, which includes big economies such as Australia, Canada, India, New Zealand and South Africa.

"You've got to look at this at a global level. I will be raising this with my Commonwealth partners," he said in a pre-summit briefing for reporters on Wednesday. Brown's office asked that his remarks not be published until Friday.

"You can look at an insurance scheme. You can look at the creation of resolution funds. You can look at asking banks to hold contingent capital. Or you can look at a transactions or a global levy of some sort," he said.

"I think I will find a great deal of support from a large number of countries around the world ... I think ... there will be gradually more support for the proposals I am putting forward," he said.

ZIMBABWE

Brown also wants the Commonwealth to dangle the carrot of re-admission before Zimbabwe to encourage reform there.

Zimbabwe withdrew from the Commonwealth in 2003 after the group of mainly former British colonies renewed a suspension imposed on the country in 2002 when President Robert Mugabe won re-election in a poll some observers said was rigged.

Mugabe and opposition leader Morgan Tsvangirai have now formed an uneasy partnership in a unity government.

Brown said the unity government had achieved changes but Britain remained concerned about the pace of progress.

"There is still a great deal to do on judicial reform, on constitutional reform, on human rights and economic reform and we are clearly not yet at a stage for Zimbabwe to rejoin the Commonwealth," he said.