(CNN) Influential Republican consultant and former Minnesota congressman Vin Weber resigned on Friday from Mercury LLC, a major DC consulting firm, amid ongoing scrutiny of his Ukranian lobbying efforts.

Weber's resignation comes amid new attention his past work has received, and while an investigation into it appears to still be unresolved. He cited publicity surrounding his past work as a nuisance to current clients in a resignation letter to Mercury's CEO Kieran Mahoney on Friday.

"As you know, there has been recent publicity relating to work that I did a number of years ago on behalf of a former client," Weber wrote. "This publicity has become a distraction for me and for the important work that Mercury is doing for its clients. With sadness, I take this action to remove the distraction for Mercury's clients and to focus my time and energy on protecting my reputation."

Former special counsel Robert Mueller's prosecutors in 2018 referred inquiries on Weber and others involved in Ukrainian lobbying work with former Trump campaign chairman Paul Manafort to the US Attorney's Office in the Southern District of New York, and other prosecutors have picked up legs of the Ukrainian case. Weber has not been charged with any crime, but another well-known Washingtonian and former White House counsel, Greg Craig, was charged for his actions related to the work and is currently nearing the end of his criminal trial next week

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