HM Revenue & Customs (HMRC) is reportedly investigating alleged tax avoidance schemes run by Barclays.

Alistair Darling signalled yesterday that he was ready to crack down on tax avoidance by Britain’s banks.

The Guardian last night published memos on its website, supposedly from Barclays’ structured capital markets division, which detail schemes allegedly to avoid tax through a series of international loans. The documents are understood to have come from a whistleblower within Barclays, who passed them to Vince Cable, the Liberal Democrat treasury spokesman.

HMRC said: “We have received papers relating to allegations of tax avoidance in the banking industry which we are studying carefully.”

Barclays said: “Project Knight was voluntarily and fully disclosed to HMRC, though there was no statutory obligation to do so.”

The Chancellor told MPs that HMRC would publish a code of practice on taxation for the banking sector around the time of the Budget next month. The code, initially voluntary, would mean that banks must comply “not just with the letter but the spirit of the law”, the Chancellor said. “We expect banks to fully comply with their tax obligations.”

Officials said that the taxpayer could save billions as a result.

Banks in which the taxpayer had a stake, including Royal Bank of Scotland and Lloyds, would come under particular scrutiny and would be expected to desist from practices that, while they may be technically legal, were totally inappropriate, officials said. Banks would be expected to comply with the code. If they did not, it could become statutory.

The code will be aimed at the banking sector as a whole and institutions applying for government insurance for their toxic debts will be told that they are expected to comply.

The scheme will be based on the one introduced for the corporate sector, in which officials engage in a “dialogue” with big companies to weed out avoidance schemes. According to the Treasury, it has resulted in billions of pounds extra in tax being collected.

Tax avoidance is legal, whereas tax evasion is illegal – but avoidance is deeply frowned upon and each year the Treasury comes up with new efforts to close loopholes.

With banks in the firing line over their role in the credit crisis, ministers clearly have decided that it is time to act. Moreover, with the G20 summit certain to insist that tax havens open up their affairs, the activities of all banks are expected to become more transparent.

There have been recent allegations of banks making as much as £1 billion a year from avoidance schemes. The avoidance schemes used by banks are particularly complicated, according to officials, and the complexity and lack of transparency involved could themselves have an impact on financial stability.

Mr Cable welcomed the proposal for a banking code of conduct, but asked why the Government could not get the banks in which it owned a share simply to stop avoiding taxes. He also repeated calls for large banking institutions to be split into high-street retail and investment divisions.

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