Washington:
US President Barack Obama released his tax return on Friday, showing that he earned nearly $800,000 last year, leveraging the annual rite to launch a new attack on his wealthy Republican foe Mitt Romney.
Cranking up their campaign for a second term ahead of November's election, Obama and Vice President Joe Biden have now made their tax returns public for each year going back to 2000.
They complain that Mr Romney, a multi-millionaire venture capitalist they are trying to portray as oblivious to the economic struggles of middle class American families, has not done the same.
Mitt Romney has released his return for 2010 and an estimate of his taxes for 2011, but has yet to do the same for previous years, including when he worked at the investment firm he founded, Bain Capital.
In 2010, Mr Romney paid a lower tax rate than many middle class Americans -13.9 per cent on income of $21.7 million. His estimated income from 2011 was $20.9 million and his fortune is estimated at about $250 million.
"Governor Mitt Romney has yet to provide tax returns from the period in which he made hundreds of millions as a corporate buyout specialist, or as governor of Massachusetts, the experience he says qualifies him to be President," said Jim Messina, Mr Obama's campaign manager.
Messina questioned if Mr Romney did not want voters to see whether he had used loopholes to avoid paying some taxes, or whether he had investments offshore.
Because most of his income was from investments and not salary, Mitt Romney is subject to different rules than most people, and is taxed at a lower rate than many middle class Americans pay on their annual income.
Mr Obama contends that such treatment of the wealthy is unfair, and is pushing a proposal called the Buffett rule, which would require people earning more than $1 million a year to pay 30 per cent in taxes.
The President's tax return showed that he and First Lady Michelle Obama reported $789,674 for 2011 in gross adjusted income and paid $162,074 to the Internal Revenue Service at an effective federal tax rate of 20.5 per cent.
Around half of Mr Obama's income came from his Presidential salary of $400,000 and the rest was from income from his bestselling books. The first couple donated $172,130 to charity, or about 22 per cent of their adjusted gross income.
Mr Biden and his wife Jill, a community college professor, reported earning $379,035 in 2011 and paid $87,900 in federal income taxes.