The Chancellor has expressed his "shock" that some of the country's wealthiest people are able to organise their finances so they pay "virtually no" income tax.
George Osborne told the Daily Telegraph he had seen "anonymised copies" of tax returns showing some of the highest earners paid just a tenth of their income in tax.
He said he believed the very wealthiest should be paying around a third.
The tax returns had been submitted to the Chancellor by HM Revenue and Customs, the Telegraph reported.
He was not given the details of the individuals involved, but he said the returns he had seen had shown him the 20 biggest tax avoiders had legally reduced their income tax bills by a total of £145m in a year.
He said: "I was shocked to see that some of the very wealthiest people in the country have organised their tax affairs, and to be fair it's within the tax laws, so that they were regularly paying virtually no income tax. And I don't think that's right."
Osborne did not outline any new measures.
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