British ministers had opposed the tax, which places a levy on some financial transactions to raise public funds, claiming that it would damage British firms, but the ECJ ruled that the UK was unable to block it for this reason.
Nigel Farage, co-chair of parliament's Europe of Freedom and Democracy Group, and head of the UK's controversial Ukip, slammed the British government's role, saying, "This FTT judgement shows that the UK cannot act to protect the UK's biggest interest.
"It is impotent and at the mercy of an antagonistic federalist court - the ECJ.
"It shows [British prime minister David Cameron's] argument that the UK government can negotiate a better deal for British business from within the EU as a fraud and a farce."
His criticism continued, "The only way to protect the UK financial interest is to withdraw from the tax-hungry EU and stop giving Brussels power over us.
"It is now clear that financial institutions in member states such as the UK and outside the FTT zone can be taxed," adding, "This is a deliberate assault on the City of London."
Turning his attention to the European commission, the outspoken deputy said, "We now have it in black and white that the European commission wants to tax financial institutions in the UK even though they are not within the FTT zone.
"The commission proposal is clearly targeted to tax financial services in the city even though the UK government does not want to be part of the participating member states.
"The UK government will have no say on this tax system, but businesses within its borders will have burdened by this FTT," he went on.
"This tax will help push financial services outside the EU altogether, to Switzerland and other growing financial centres around the globe.
"Mark my words, this taxation is just the beginning because the FTT tax rate will be ratcheted up over the coming years to squeeze more money from the financial services industry.
"Just how many times does the British financial industry have to be kicked in the teeth by the ECJ before Cameron will shout 'enough is enough," concluded Farage.
However, Greens/EFA deputies Keith Taylor and Jean Lambert took a very different view on the matter.
Taylor said, "[This] decision by the European court of justice is the right one," adding, "The [FTT], which will redistribute money from the world of finance to those in need, is unsurprisingly opposed by the government and their friends in the banks.
"This defeat for the City of London, and significant win for campaigners, takes us one step closer to introducing the [FTT] in Europe.
He continued, "It's now time for the British government to wake up to the fact that this tax is popular, redistributive and fair and should be introduced to the UK too.
"We must not let the spotlight on finance fade. The financial transaction tax goes some way towards making finance fairer, but much work is still to be done," urged Taylor.
While his London Greens colleague also agreed with the outcome, saying, "This ruling is really about whether or not we want to support speculative casino banking with billions of pounds of public money when the bankers get it wrong.
"In 2008, they got things spectacularly wrong, and we are all still paying the price with recession and government austerity measures."
She explained, "A 'Robin Hood' tax would slow down the gambling - and raise revenue for public services at the same time. I can see why the French and German governments have embraced the idea.
"I welcome this ruling, which takes us down the road of delivering the more people-centred banking industry the Greens in Brussels are working hard for," said Lambert.