They call it the Robin Hood tax — a tiny levy on trades in the financial markets that would take money from the banks and give it to the world’s poor.

And like the mythical hero of Sherwood Forest, it is beginning to capture the public’s imagination.

Driven by populist anger at bankers as well as government needs for more revenue, the idea of a tax on trades of stocks, bonds and other financial instruments has attracted an array of influential champions, including the leaders of France and Germany, the billionaire philanthropists Bill Gates and George Soros, former Vice President Al Gore, the consumer activist Ralph Nader, Pope Benedict XVI and the archbishop of Canterbury.

“We all agree that a financial transaction tax would be the right signal to show that we have understood that financial markets have to contribute their share to the recovery of economies,” the chancellor of Germany, Angela Merkel, told her Parliament recently.

On Sunday, Mario Monti, the new prime minister of Italy, announced plans to impose a tax on certain financial transactions as part of a far-reaching plan to fix his country’s budgetary problems, and he endorsed the idea of a Europewide transactions tax.