Image caption The Romney campaign had previously estimated his 2011 taxes at 15.4%

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

Mr 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 US is 35%, but Mr Romney lives mainly on income derived from his investments, for which only 15% tax is payable.

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

Mr 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 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 taxes

The move came amid attempts by the Romney campaign to shift the focus of recent days away from remarks he made at a private donor dinner.

In the video secretly recorded earlier this year, he disparages Obama voters, saying they pay no income tax.

Mr Romney's critics say he should follow the example of his father, former Michigan Governor George Romney, who released a dozen years of tax returns during his own unsuccessful run for president in 1968.

But the former Massachusetts governor has said he is following 2008 Republican White House candidate John McCain's example of releasing two years of taxes.

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

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

As he released his 2010 return in January this year, Mr Romney said he had paid "all the taxes that are legally required and not a dollar more".

But according to Brad Malt, the trustee that controls Mr Romney's wealth as he runs for president, the Romneys donated $4m to charity in 2011, claiming $2.25m of it as a deduction.

"The Romneys thus limited their deduction of charitable contributions to conform to the Governor's statement in August, based upon the January estimate of income, that he paid at least 13% in income taxes in each of the last 10 years," Mr Malt said.

The campaign has stressed that the blind trust run by Mr Malt means that the candidate is making no decisions on how his money is invested.

Tax law experts say the release of the 2011 return - and the summary of the past 20 years - will do little to silence questions about Mr Romney's past tax liability, including the source of a $100m retirement account and the tax advantages of his offshore investments.