U.S. President Barack Obama is telling his Republican rival for the White House, Mitt Romney, that he cannot “just make stuff up.”

During an appearance at the White House briefing Monday, Mr. Obama said Romney's charge that the president dropped a requirement for welfare recipients to work is “patently false.”

President Obama also repeated his call that Romney release more of his tax returns. The president said the lives of those seeking the White House are an open book and that releasing tax returns has become part of the campaign.

Two years of tax records show Romney has Swiss bank accounts. The president said he in no way suggests Romney has done anything illegal. But he said the average American does not use overseas accounts to manage tax obligations.

Romney and his choice for vice president, Paul Ryan, campaigned Monday in New Hampshire, verbally attacking Mr. Obama's policies on Medicare and the economy.

The challenger also accused the president of lying when he said Romney would cut taxes for the rich and raise them for the middle class. Romney said no one's taxes would go up if he is president.

A new poll shows that a majority of voters in 12 key U.S. swing states feel they are worse off than they were four years ago, yet still support President Obama over Mitt Romney.