UK’s big four banks – Barclays, HSBC, the Royal Bank of Scotland (RBS), and Lloyds – are among the most prolific users of tax havens, according to new research published by ActionAid, which raises fresh concerns about the full extent of corporate tax avoidance.

According to the new data published by the charity, the UK’s 100 biggest public companies are running more than 8,000 subsidiaries or joint ventures in onshore and offshore tax havens, and only two of the companies listed on the UK’s FTSE 100 have no subsidiaries in tax havens.

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HSBC reportedly has 496 subsidiaries in tax havens, according to the new ActionAid research, while RBS has 393 subsidiaries in tax havens.

Lenders such as Barclays, reportedly, own "hundreds" of subsidiaries in onshore and offshore tax havens. According to Barclays, in 2011 it was working to cut the number of its offshore subsidiaries in the Caymans, but the research shows it still had more than 120 subsidiaries in the region, along with dozens of others in other overseas jurisdictions with low tax rates or limited disclosure rules to other tax authorities.

A Barclays spokesperson told The Guardian, the lender was among the UK’s "top taxpayers and acted ethically".

She said: "Barclays has substantial businesses in many of the jurisdictions mentioned.

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"In the Caymans virtually all of the profits generated in these companies are subject to corporate tax at the UK corporate tax rate. The number of Barclays’ entities in low-tax jurisdictions reduced from 339 in 2009 to 252 by February 2013 – a 26% reduction. We plan to make further reductions in 2013."

In total, FTSE 100 companies have 1,685 subsidiaries in UK Crown dependencies such as Jersey, or overseas territories such as the British Virgin Islands (BVI), Bermuda and Gibraltar.

The UK Treasury recently secured a deal to share more information on potential income-tax evaders operating out of British overseas territories.

The research has also compiled data covered by a wider definition of tax haven, including onshore jurisdictions such as the US state of Delaware, and the Republic of Ireland.

At the meeting of G7 finance ministers on 11 May, the UK chancellor, George Osborne, said international action was needed, adding it was "incredibly important that companies and individuals pay the tax that is due".

ActionAid’s tax justice policy adviser, Mike Lewis, who conducted the research, called tax havens "one of the biggest hidden obstacles" in the fight against global poverty.

He added: "Poor countries lose three times more money to tax havens than they receive in aid each year.

"Tax haven structures are almost universal amongst the UK’s biggest multinationals and becoming ever more common for investments in developing countries."