Fibbing on your resume is a really bad idea.

First, you probably will be found out by the army of commercial background screeners that employers deploy to scour resumes, check criminal records and pull credit histories.

Plus, you don’t need to. Many bosses are pretty forgiving if you come clean about a minor brush with the law or a supervisor so nutty he sent you running for the door.

Yet, resume tinkering is practically an epidemic. Superheated competition for jobs, especially those with big paychecks, tempts many applicants to pump air into their resumes. A gig as an administrative assistant expands into a management title. A mail-order MBA is passed off as the real deal.

“We tend to disproportionately reward individuals with extraordinary records,” said Kirk Hanson, a business professor and executive director of the Markkula Center for Applied Ethics at Santa Clara University in California.

“There’s a huge incentive that’s increased over the years in claiming that you’re a star, so individuals tend to knock pieces from their resume that are inconsistent with being a star and add things that are consistent with that image.”

But the precipitous tumble of high-profile managers in recent years should send up red flags for job seekers.

Marilee Jones had to quit her job as the longtime admissions dean at the Massachusetts Institute of Technology after acknowledging that she didn’t have an undergraduate degree as she had claimed. Jones had won national attention crusading against the pressure on students to build their resumes for elite colleges.

David Edmondson’s 11-year career with RadioShack Corp. tanked in 2006, when misrepresentations he had made about his education came to light. He had been the company’s president and chief executive.

They are hardly alone.

An annual employer survey turned up “inconsistencies” in the work histories of nearly half of job seekers last year, with 20 percent of applicants providing false or misleading information about their educational credentials. Discrepancies in verifying past employment were up 12 percent over 2005 and up 7 percent involving education, the poll by Kroll Background Screening and Fraud Solutions showed.

“It’s astonishing to me the kind of things that people try to fabricate,” said Scott Viebranz, Kroll’s chief sales officer. “They don’t believe it will be found.”

Job hunters should be forgiven for feeling like they are criminals before they even get to the interview. But increasingly, employers are looking to protect their reputations and deflect any liability if they unwittingly hire a crook or a fraudster. So job offers routinely come with a big string attachedpassing a background screen.

PricewaterhouseCoopers recruiters thought they had bagged a terrific job candidate until a check found he hadn’t attended the college where he said he had earned his undergraduate degree.

“We gave him a chance to provide documentation,” said Jennifer Allyn, a human resources manager for the accounting giant. “He said he was in some dispute with the school and concocted a whole story that made no sense.”

The company rescinded the offer. Often, what job seekers leave off their application causes them more problems than what they put on it.

“It’s what they didn’t tell you, that they filed for bankruptcy or sued a former employer or had been sued,” said Kenneth Springer, president of New York-based Corporate Resolutions Inc., another commercial screening firm.

Fessing up always is better than staying silent.

Rick Hammond remembers a promising candidate who failed to disclose a long-ago drunken-driving conviction.

“It wouldn’t have been a deal-breaker if he’d disclosed it,” said Hammond, the president of Rhumbline Cos., a Los Angeles placement agency for accounting and legal professionals. But the applicant was out of the running once a background check turned up the old offense.