Republican presidential candidate Mitt Romney has released tax records, indicating he will pay $5.9 million in taxes on a total of $43 million in income over the years 2010 and 2011.

Bowing to increasing political pressure to provide more detail about his vast wealth, the former private equity executive released tax details showing he and his wife, Ann, paid an effective tax rate of 13.9 per cent in 2010.

They expect to pay a 15.4 per cent rate when they file their returns for 2011.

Mr Romney's tax rate is below that of most wage-earning Americans because most of his income, as outlined in more than 500 pages of tax documents, flows from capital gains on investments.

Under the US tax code, capital gains are taxed at 15 per cent compared with a top tax rate of 35 per cent for wage earners.

Mr Romney released the returns after a week in which his chief rival for the Republican presidential nomination, former House speaker Newt Gingrich, questioned whether Mr Romney was hiding information about his finances and cast him as being out of touch with most Americans.

Mr Gingrich's attacks on Mr Romney helped him upset the former Massachusetts governor in the South Carolina primary on Saturday.

Since then Mr Romney has vowed to be more aggressive in returning fire.

He has launched a series of attacks questioning Mr Gingrich's character, judgment and lucrative work as a Washington consultant, and released his tax returns to try to nullify Mr Gingrich's criticisms.

Fairness debate

The tax rates Mr Romney reported paying could add fuel to a national debate over the fairness of the tax code and coincides with broader concerns about income inequality symbolised by the Occupy Wall Street movement.

Mr Romney's campaign officials stressed his tax rate was based mostly on income from investments that were held in a blind trust.

The holdings include an undisclosed amount in funds based in the Grand Cayman Islands and other overseas entities.

Romney advisers stressed the holdings in the Caymans - along with those in a Swiss bank account that was closed in 2010 after an investment adviser decided it could be politically embarrassing - were reported on tax returns and were not vehicles to avoid taxes.

They also stressed Mr Romney, whose holdings are in three blind trusts, makes no decisions as to how his money is invested.

Regardless, the emerging picture was of a man of great means who contributes mightily to charity. The documents showed he and his wife contributed almost $7 million in charity over the two years, much of it going to his Mormon church.

Mr Romney, whose estimated net worth is as much as $238 million, is among the wealthiest Americans to ever seek the presidency.

Reuters