Republican Representative Chris Collins is resigning ahead of his expected guilty plea to corruption charges, CBS News has confirmed.

Collins submitted his resignation letter Monday to House Speaker Nancy Pelosi's office. The resignation will become official on Tuesday, according to a senior aide familiar with the congressman's decision.

Collins, the first member of the House to back Donald Trump for president, is expected to plead guilty to insider trading charges in New York on Tuesday. Collins' abrupt departure will spur a special election in New York's 27th district. Collins has been in Congress since 2013.

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Collins was indicted in August 2018, accused of using inside information about a biotechnology company to help his son make illicit stock trades. The indictment charged Collins, the congressman's son, and the father of his son's fiancee with conspiracy, wire fraud and other counts.

One of the most pivotal moments in the prosecution's case actually, allegedly, took place at the White House picnic in 2017. CBS News' Sara Cook and Arden Farhi uncovered video of Collins on the phone, at what appears to be the same time federal investigators claim Collins was making a call to his son to tell him to sell stock in Australian biotech company Innate.

Rep. Chris Collins on phone at Congressional picnic at White House, June 2017 screen grab / Sara Cook

Ed O'Keefe contributed to this report.