A bitter row has broken out between US President Barack Obama and his Republican rival for the White House, Mitt Romney, over whether Mr Romney was involved in moving American jobs overseas.

Mr Obama's campaign team says it has uncovered papers showing Mr Romney was in charge of the private investment firm, Bain Capital, when it invested in companies which were outsourcing jobs.

Mr Obama's deputy campaign manager Stephanie Cutter also said he might have committed a felony by giving wrong information to the Securities and Exchange Commission about how long he spent at Bain.

Mr Romney struck back, demanding an apology from Mr Obama for suggesting he may have committed a felony.

"It's ridiculous," Romney told Fox News in response to the charge. "And of course it's beneath the dignity of the presidency and of his campaign."

The Republican challenger has appeared flatfooted in beating back Democrats' accusations that he was involved in firing workers and outsourcing US jobs to foreign countries while at Bain Capital.

Mr Romney has slipped in opinion polls ahead of the 6 November election and his campaign added two Washington veterans to its media relations team after criticism from fellow Republicans for communications missteps.

He was booed by a mostly black audience at the NAACP annual convention this week and earlier gave out mixed messages about whether a key part of Mr Obama's healthcare law does or does not create a new tax.

The row over Bain Capital is the latest issue to distract Mr Romney from his focus on Mr Obama's failure to reduce unemployment, running at 8.2%.

Two national polls this week showed Obama opening up a wider gap over his opponent. A Reuters/Ipsos survey had the former Massachusetts governor trailing the incumbent by 6 points, although other polls have them in a closer race.