The public will never be told what rate of tax Google has paid as part of its controversial £130m settlement.

The news emerged as UK ministers were accused of offering the tech giant “mate’s rates” and a “sweetheart deal”.

At the weekend the Chancellor hailed the agreement, which covers the last decade, as a "major success".

David Gauke, the Financial Secretary to the Treasury, who was dragged to the Commons to answer questions on the arrangement after Labour tabled an urgent question, told MPs Google had not secured a “special” tax break only available to some firms.

He also rejected claims of an effective 3 per cent rate of tax.

But he said that "taxpayer confidentiality" meant that he could not confirm what rate the global search engine had paid.

Asked specifically if Google had broken any laws, he added: “I cannot comment in large part because I'm not privy to information that is not in the public domain".

Labour’s shadow Chancellor John McDonnell criticised Mr Osborne for not coming to the Chamber himself to answer questions from MPs.

Mr McDonnell also accused the Tories of "confusion" over the deal, with Osborne initially hailing it as a "major success", Downing Street describing as a "positive step forward" and London Mayor Boris Johnson labelling it "derisory".

Google, which reached the settlement with tax officials at HMRC, has also agreed to also start to pay tax "based on revenue from UK-based advertisers, which reflects the size and scope of our UK business".

Critics have long questioned Google's tax bill.

In 2013 UK sales were valued at £3.8 billion, but the company paid just £20.4m in taxes.

In the Commons Stewart Hosie, the SNP's economy spokesman, questioned if the deal should have been put to Margrethe Vestager, European commissioner for competition, "to ensure that it complies with state aid rules... given the difficulty the Netherlands got in with a deal over Starbucks and Luxembourg did with the deal over Fiat, when the (European Commission) insisted they recoup between 20 million and 30 million euros extra."

Andrew Tyrie, the Conservative chairman of the Treasury Select Committee, suggested that "fundamental reform" of the tax base might be required.

His committee later announced details of an inquiry into the tax base, entitled 'shifting sands'.

Google said that the settlement reflected a shift in the international tax system "and is in line with recent OECD guidance".