The Moody’s credit-rating agency has been widely blamed for contributing to the financial bubble and its devastating implosion by giving high grades to dubious investments.

Now one of its own is leading the criticism.

In an 80-page letter to federal regulators, a former Moody’s senior vice president says the firm systematically squelched its analysts’ private doubts to keep deals and profits flowing.

Moody’s managers intimidated analysts who stood in the way of favorable ratings, and its compliance department harassed employees who took an independent stand, according to the former analyst, William J. Harrington.

According to Harrington, a fundamental conflict of interest permeated the firm’s culture: Like other credit rating agencies, Moody’s is paid by the very companies whose securities it is supposed to grade objectively.

“Moody’s incentivized an analyst to accede to all items demanded by an external paymaster and to work to the paymaster’s schedule,” Harrington wrote.

“The goal of management is to mold analysts into pliable corporate citizens who cast their committee votes in line with the unchanging corporate credo of maximizing earnings of the largely captive franchise,” he wrote.

Repeatedly, Moody’s management ignored internal warnings that employees responsible for rating securities backed by home mortgages were “pumping out worthless opinions,” he wrote.

Asked to respond to Harrington’s letter, a Moody’s spokesman defended the firm’s work. “We cannot emphasize strongly enough the importance Moody’s places on the quality of our ratings and the integrity of our ratings process,” spokesman Michael N. Adler said in a statement.

“For that very reason, we have robust protections in place to separate the commercial and analytical aspects of our business, and our ratings are assigned by a committee — not by any individual analyst,” Adler added.

Harrington says Moody’s management subverted the objectivity of the committees, partly by belittling opposing views.

A committee member who votes in keeping with personal objections “courts retaliation from management,” Harrington wrote. As a result, he said, the opinions Moody’s published for public consumption “are often at odds with its private opinions.”

Harrington expressed his views in a recent letter to the Securities and Exchange Commission, which at the behest of Congress is drafting new rules for credit-rating agencies.

Moody’s management and board “are squarely responsible for the poor quality of previous Moody’s opinions that ushered in the financial crisis and should not be given first shot at debasing future opinions as well,” he said.

His letter was the subject of an article Friday on the Web site Business Insider.

Harrington wrote that he was an analyst in the Moody’s group that rated derivatives from 1999 until he resigned last year.

In 2009 and 2010, the Moody’s compliance department raised “trumped-up” disciplinary charges against him, which dovetailed with work he was doing that could affect a transaction between Merrill Lynch and AIG, the insurance company that received a federal bailout in 2008, he said.

Until 2010 Harrington said he received “very high” performance ratings for his “ability to work on difficult transactions” and “analytical capabilities.” Yet, he said, a recurring theme ran through his reviews: He should “make life easier for bankers” and companies that issue securities. And “he should be more alert to the bottom line.”