Republican presidential candidate Mitt Romney has released his much-anticipated 2011 tax return, which shows he paid a rate of 14.1%, BBC News reported.

Romney paid $1.9m (£1.1m) in taxes in 2011, on $13.7m of income.

The private equity tycoon has already released his 2010 tax return, for which he paid about $3m, a 13.9% rate.

The top rate of income tax in the U.S. is 35%, but Romney lives mainly on income derived from his investments, for which only 15% tax is payable.

Critics, including President Barack Obama, whom Romney will challenge for the White House in November, have called on him to release more tax returns.

Romney's 2011 tax rate of 14.1% compares with a previous estimate of 15.4% for the year by his aides. The Romneys filed their 2011 return with the Internal Revenue Service on Friday, Sept 21, after applying for an extension earlier in the year.

The campaign also released a letter from his accountants with a summary of his returns from 1990-2009, which said he paid an effective average of 20.2% over the period, with the lowest return at 13.66%.

Obama's 2011 tax return showed he paid an effective rate of 20.5%, on an income of $789,674.

On average, U.S. middle-income families, those making from $50,000 to $75,000 a year, pay 12.8%, according to congressional research.