Jack Welch, the lionised former chairman of General Electric Co, provoked cries of outrage in Washington on Friday when he appeared to accuse the White House of manipulating September job figures for political gains.

White House officials dismissed as 'ludicrous' a tweet Welch sent to his more than 1.3 million followers that suggested US President Barack Obama's administration rigged the data as a way of recovering from a poor Wednesday night showing in a debate against Mitt Romney, his Republican challenger for the White House.

"Unbelievable jobs numbers..these Chicago guys will do anything..can't debate so change numbers," Welch said in a posting on Twitter, apparently referring to Obama, who formerly served as a senator from Illinois.

The tweet was repeated more than 2,000 times, with many mocking posts comparing Welch to New York real estate tycoon Donald Trump - who during his failed bid for the presidency loudly argued that Obama was not born in the United States - and Clint Eastwood, who gave a widely panned speech to an empty chair at the Republican National Convention in August.

Officials in Washington quickly dismissed the idea that the Labor Department report - which showed US unemployment falling to a four-year low of 7.8 per cent - could be rigged.

"That's a ludicrous comment. No serious person believes that the bureau of labor statistics manipulates its statistics," said Alan Krueger, chairman of the White House Council of Economic Advisers.

"The jobs report and all of their other statistics are prepared by career employees. They use the same process every month. They use the same process for Republican and Democratic administrations.''

The tweet was by no means Welch's first criticism of Obama on his Twitter feed, where he has regularly spoken out in favor of Romney, as well as weighing in on sports.

During the presidential debate in Denver, Colorado, on Wednesday night, Welch tweeted: "HOW can anyone vote for Obama after this performance..he has demonstrated his incompetence."

MEMORIES OF THE 'BLACK BOX'

Welch's comments drew particular fire from the financial community since during his 20-year tenure as GE CEO, which ended in 2001, he was accused of using the GE Capital finance unit as a 'black box' where he could quickly sell assets such as real estate to ensure that the largest US conglomerate regularly beat Wall Street profit estimates by a penny.

"This guy is the guy that's telling me the books are cooked? That's hilarious," said Barry Ritholtz, CEO and director of equity research at Fusion IQ in New York, which manages about $300 million in assets. Ritholtz was one of the first to respond to Welch's tweet.

Other tweets agreed with Welch's assertion. Welch is a frequent participant on the site and has more than 1.3 million followers.

"In regards to today's Jobs report---I agree with former GE CEO Jack Welch, Chicago style politics is at work here," said Florida Representative Allen West, a Republican, on Twitter.

GE Capital grew to generate about half of the Fairfield, Connecticut-based company's earnings under Welch. But the operation's vulnerabilities became all too clear during the financial crisis, when losses at GE Capital hammered the company's earnings and sent its stock below $6.

Welch's successor Jeff Immelt, who has been working to scale back GE Capital and make it less volatile, serves as top adviser to the Obama administration on jobs and the economy. GE officials declined to comment on Welch's words.

Welch, who with his wife Suzy Welch, writes a column for Reuters, could not be reached to comment further on his view.

BLS DEFENDS METHODS

Officials with the Bureau of Labor Statistics defended their methods and findings.

"We have done a monthly survey since 1940 and the methods have broadly not changed," said Karen Kosanovich, an economist with the bureau.

"Fiddling with the numbers, I don't know how that would be possible."

US Labor Secretary Hilda Solis told CNBC television that she was 'insulted' by the remark.

Other economists said they regarded the idea that the monthly data - which is widely watched by Wall Street, particularly in the face of the United States' slow recovery - could be rigged as strange.

"Because we lost two-tenths (of a percentage point) last time and three-tenths this time, the conspiracy theorists would contend the BLS is cooking the numbers," said Ray Stone, an economist with Stone & McCarthy Research Associates in Princeton, New Jersey.

"This just isn't true. They don't do that."