A coalition of charities, aid groups, unions, and movie actors and directors has launched a campaign calling for a global 0.05 percent tax on banks’ speculative financial transactions, with the proceeds going to combat poverty and climate change.

The campaign, based in the United Kingdom, expands on recent proposals for a so-called “Tobin Tax,” named after Nobel-winning economist James Tobin. A tax on financial transactions has recently attracted support in Europe from British Prime Minister Gordon Brown, German Chancellor Angela Merkel and French President Nicolas Sarkozy. However, in the U.S., Treasury Secretary Timothy Geithner rejected such a tax last November, saying, “A day-by-day financial transaction tax is not something we’re prepared to support.”

The “Robin Hood Tax” is the latest version of the proposal. Among the supporters are aid organizations such as Comic Relief, Housing Justice, ONE, Oxfam, the Salvation Army and Unicef.

The campaign also has a Web site, www.robinhoodtax.org, with a YouTube video (shown below) featuring actor Bill Nighy, who appeared in the “Pirates of the Caribbean” movies, directed by “Four Weddings and a Funeral” screenwriter Richard Curtis. The group believes it could raise hundreds of billions of dollars a year from the tax.