A US report has claimed the UK's Financial Services Authority "hampered" an official investigation into money laundering allegations against banking giant HSBC and that Chancellor George Osborne sought to influence the inquiry.
HSBC was not prosecuted over the allegations in the US because officials were concerned it would cause a global financial disaster, according to the report.
The bank was instead fined £1.2 billion by the US authorities in 2012 in a settlement.
The report, "Too big to jail: Inside the Obama Justice Department's decision not to hold Wall Street accountable", names Mr Osborne as having intervened in the US investigation by sending a letter in September 2012 to the chairman of the Federal Reserve.
It says: "Chancellor Osborne insinuated in his letter of September 10th that the US was unfairly targeting UK banks by seeking settlements that were significantly higher than 'comparable' settlements with US banks."
The report is by Republican staff of the committee on financial services in the US House of Representatives, which is chaired by Republican Jeb Hensarling.
It claims: "Rather than lacking adequate evidence to prove HSBC's criminal conduct, internal Treasury documents show that DOJ leadership declined to pursue AFMLS's recommendation to prosecute HSBC because senior DOJ leaders were concerned that prosecuting the bank 'could result in a global financial disaster' -- as the FSA repeatedly warned."
In the executive summary it said: "The involvement of the United Kingdom's Financial Services Authority in the US government's investigations and enforcement actions relating to HSBC, a British-domiciled institution, appears to have hampered the US government's investigations and influenced DOJ's decision not to prosecute HSBC."