A European tax on financial transactions could cost Britain's economy up to 20 times the amount it raises, a committee of lawmakers said on Friday.

Britain has said a transaction tax, dubbed a Tobin Tax after the U.S. economist who devised it in the 1970s, would only work globally and the EU plans are deeply confused.

Britain is fiercely opposed to the proposed financial transaction tax (FTT), which the European Union said could raise 57 billion euros (49 billion pounds) a year if implemented across the bloc.

The FTT is likely to induce a loss in GDP between five and 20 times larger than the revenues raised from the tax, according to an economic sub-committee of the House of Lords, the upper chamber of the parliament.

The sub-committee is conducting an inquiry into the impact of an FTT, and said the proposal would have profound implications for Britain by forcing businesses to relocate overseas or see revenues moving from London to elsewhere.

The EU's executive European Commission adopted plans in September for the tax from 2014, but it needs unanimous approval from all EU states.

Under the plan, stock and bond trades would be taxed at the rate of 0.1 percent, with derivatives at 0.01 percent.

Britain has said a transaction tax, dubbed a Tobin Tax after the U.S. economist who devised it in the 1970s, would only work globally and the EU plans are deeply confused.

(Reporting by Steve Slater)