Jack Welch, the former CEO of General Electric, is elaborating on his tweet last week voicing suspicion that the Obama administration is manipulating U.S. employment data for political advantage.

"Unfortunately for those who would like me to pipe down, the 7.8 percent unemployment figure released by the Bureau of Labor Statistics (BLS) last week is downright implausible. And that's why I made a stink about it," Welch said in an Op-Ed in the Wall Street Journal today.

The U.S. unemployment rate unexpectedly fell to a near four-year low of 7.8 percent in September, from 8.1 percent in August and 8.3 percent in July, the BLS reported Friday. the lowest since President Obama took office. Most economists were expecting a slight rise, but other than some GOP hardliners, economists and Wall Streeters dismissed the manipulation suggestion out of hand.

"Unbelievable jobs numbers…these Chicago guys will do anything…can't debate so change numbers," Welch, 76, and a Republican tweeted minutes after the announcement.

Today, Welch, who was at the helm of GE for more than 25 years, wrote that "If I could write that tweet again, I would have added a few question marks at the end to make it clear I was raising a question."

"The Obama campaign and its supporters, including bigwigs like David Axelrod and Robert Gibbs, along with several cable TV anchors, would like you to believe that BLS data are handled like the gold in Fort Knox, with gun-carrying guards watching their every move, and highly trained, white-gloved super-agents counting and recounting hourly," Welch wrote today.

"Let's get real. The unemployment data reported each month are gathered over a one-week period by census workers, by phone in 70% of the cases, and the rest through home visits. In sum, they try to contact 60,000 households, asking a list of questions and recording the responses.

"The possibility of subjectivity creeping into the process is so pervasive that the BLS's own "Handbook of Methods" has a full page explaining the limitations of its data, including how non-sampling errors get made, from "misinterpretation of the questions" to "errors made in the estimations of missing data."

Bottom line: To suggest that the input to the BLS data-collection system is precise and bias-free is-well, let's just say, overstated."

Experts told ABC News last week that it's near impossible for BLS to have manipulated the numbers. As former Bush White House aide Tony Fratto put it, " BLS is not manipulating data. Evidence of such would be a scandal of enormous proportions & loss of credibility."

"I would be very skeptical of any claims the job statistics are manipulated," Gary Burtless, an economist at the Brookings Institution, in Washington, D.C., told ABC News. "If they were, the administration's record so far in 2012 would undoubtedly look a lot brighter."

Welch says he's not sorry for the stir he caused. "I'm not the first person to question government numbers, and hopefully I won't be the last. Take, for example, one of my chief critics in this go-round, Austan Goolsbee, former chairman of the Obama administration's Council of Economic Advisers. Back in 2003, Mr. Goolsbee himself, commenting on a Bush-era unemployment figure, wrote in a New York Times op-ed: "the government has cooked the books."