UPDATE 1-UK's Brown-transaction tax just one option for banks

(Adds details on weekend proposals)

LONDON, Nov 10 (Reuters) - British Prime Minister Gordon Brown said on Tuesday banks must be made to act responsibly but that a levy on transactions was only one possible way of achieving this.

Brown floated, to a weekend meeting of G20 finance ministers, a series of ways of getting banks to start repaying some of the enormous cash injections they have received over the last year and build up funds to deal with future bailouts.

The U.S. and Canada, however, both voiced strong opposition to one of the ideas -- a tax on financial transactions that has already been championed by Germany and France. Some British newspapers have judged that a defeat for Brown.

"I think if you read my speech on Saturday, what I was talking about was the social responsibility of financial institutions," Brown said at his regular news conference.

"And we've found also that in good times the banks achieve very high rewards and in bad times it has been the country, the nation's taxpayers as a whole, who have had to underpin the banking system," he added.

Britain has pumped billions of pounds into bailing out Royal Bank of Scotland (RBS.L) and Lloyds Banking Group (LLOY.L).

Brown's calls for banks to give something back chime with comments from France and Germany, but the idea of a transaction levy has long been opposed by the United States.

U.S. Treasury Secretary Timothy Geithner said at the weekend Washington could not support a tax on day-to-day transactions, though it left the door open to other ways to protect taxpayers from losses. Canada was also lukewarm.