One day after he submitted his letter of resignation to Gov. Andrew Cuomo, Rep. Chris Collins, R-N.Y., on Tuesday pleaded guilty in a Manhattan courtroom to insider trading charges.

In a major about-face for the embattled politician, Collins pleaded guilty to charges that he passed along secrets to his son, Cameron, and his son's prospective father-in-law, Stephen Zarsky, about an Australian biotechnology company where he sat on the board.

Collins, who surrendered to federal agents in August 2018, had previously maintained his innocence and just last month pleaded not guilty to a slew of charges brought against him in a superseding indictment.

In his hearing, Collins told U.S. District Judge Vernon Broderick that he was sorry for what he'd done, but added that there was nothing he could change.

"I'm embarrassed and dismayed,” Collins said.

Collins faces up to five years in prison, followed by three years of supervised release.

NEW YORK REP. CHRISTOPHER COLLINS INDICTED ON INSIDER TRADING CHARGES

A new indictment against Collins streamlined the charges against him by keeping only five of the original eight securities fraud counts from the original. The new indictment also dropped two of the original eight securities fraud charges against the congressman's son while leaving the remaining charges in place.

"The government has made these modifications in the original indictment in an effort to avoid unnecessary pretrial litigation that could delay the resolution of the matter," Geoffrey S. Berman, the U.S. attorney for the Southern District of New York, wrote in a recent letter to the judge in the case.

The fraud counts against Collins relate to securities of a company called Innate Immunotherapeutics; the 69-year-old former congressman served on the board.

NEW YORK'S COLLINS RESIGNS HOUSE SEAT AHEAD OF EXPECTED GUILTY PLEAD FOR INSIDER TRADING

Prosecutors allege Collins passed along secrets to his son in June 2017. They say the son traded on the inside information and passed it to Zarsky, who is said to have traded on it and tipped off at least three others.

Prosecutors said the three avoided more than $768,000 in losses by trading ahead of the public announcement of some failed drug trials.

The advocacy group Public Citizen filed a request for an investigation of Collins' stock dealings with the Office of Congressional Ethics and the Securities and Exchange Commission in January 2017.

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The congressman, who has served New York's 27th District since 2013, surrendered to federal agents in Manhattan in August 2018.

Following the charges brought against Collins last year, then-House Speaker Paul Ryan removed Collins from his post on the House Energy and Commerce Committee and called the insider trading charges "a clear violation of the public trust."

Collins has a track record of publicly backing Trump, including being one of the first sitting members of Congress to endorse his White House candidacy.

Fox News' Marta Dhanis contributed to this report.