WASHINGTON, USA (AFP) — The Wall Street Journal launched a scathing rebuke of Republican Mitt Romney yesterday, saying "confusion" over his position on a health care mandate could cost him the election against President Barack Obama.

The conservative, pro-business paper said the Romney campaign was "slowly squandering a historic opportunity" by failing to produce a coherent, unified position on the Obama-backed mandate which requires Americans to obtain health insurance or pay a fine.

Romney pushed through his own health-care reforms while governor of Massachusetts, and he deemed the individual mandate which he supported in that plan a "penalty".

After the Supreme Court ruled that the health care law was constitutional under Congress's power to levy taxes, a top Romney advisor said Monday it was "correct" that Romney agrees with the president and believes the mandate's fine should be called a penalty and not a tax.

Romney on Wednesday sought to unify his campaign message, but in conceding last week's ruling and saying the mandate was a "tax" after all, he stumbled badly, the Journal said.

The candidate failed to elaborate on the tax-versus-penalty issue, and the newspaper offered a blistering critique, saying "Romney's tax confusion" looked "politically dumb."

"If Mitt Romney loses his run for the White House, the turning point will have been his decision Monday to absolve President Obama of raising taxes on the middle class," the Journal's opinion piece began.

"In a stroke, the Romney campaign contradicted Republicans throughout the country who had used the Chief Justice's opinion to declare accurately that Mr Obama had raised taxes on the middle class."

The paper said Romney made the "unforced error" because he did not want to be pinned as a flip-flopper, a label that stuck during the Republican primaries when rivals attacked him for changing positions on issues like abortion.

"The tragedy is that for the sake of not abandoning his faulty health-care legacy in Massachusetts, Mr Romney is jeopardising his chance at becoming president," the Journal said.

It also took issue with Romney's "insular" campaign staff which "thinks it can play it safe and coast to the White House by saying the economy stinks and it's Mr Obama's fault."

The Wall Street Journal is owned by News Corp, whose chief executive Rupert Murdoch on Sunday tweeted a much-discussed warning to Romney.

Murdoch wrote on Twitter that Romney ought to hire some "real pros" and "get on the front foot soon" if he wants to defeat Obama in November.

The Journal said Romney, currently on a week-long break from the campaign, and his staff were enabling Obama's attacks on Romney as an out-of-touch multi-millionaire.