The most prominent Democratic lobbyist in Washington, whose brother served as campaign chairman to Hillary Clinton, has stepped down from the firm he created after being ensnared by the Russia-Trump investigation led by Robert Mueller.

Tony Podesta, who has donated millions of dollars to the Democratic party and lawmakers on Capitol Hill and worked as a link between corporate America and the Democratic establishment, has reportedly stepped down from his lobbying firm after it emerged that the US special counsel was investigating his work for a Ukrainian not-for-profit group linked to Paul Manafort.

Podesta’s brother, John Podesta, served as Hillary Clinton’s campaign chairman and was a victim in the hacking attack against the Democratic candidate’s campaign.

Among hundreds of emails that were hacked from the Clinton campaign and later released by WikiLeaks – a crime that lies at the heart of the Russia investigation – were emails sent by John Podesta. One email from the known foodie included a detailed description of his secret to a good, creamy risotto.

News of Tony Podesta’s resignation, which was first reported by Politico, was revealed on the same day that Manafort, Trump’s former campaign chairman, and his associate Rick Gates, were charged in a multi-count indictment alleging conspiracy against the US and money laundering. A third official, a campaign adviser named George Papadopoulos, pleaded guilty to lying to the FBI and is cooperating with investigators.

Podesta has not been charged with a crime. He declined to comment to the Guardian after being reached on his mobile phone.

The Democratic lobbyist’s departure may come as a blow to some Democrats on Capitol Hill, but it also demonstrates the far reach of Mueller’s investigation.

Any potential charges against Podesta, who reportedly told staff that he did not intend to “go quietly”, could make it harder for Republicans to accuse Mueller of politicising the Trump investigation by only targeting Republicans.

But Podesta’s decision to step down, and any potential legal issues in his future, will be embarrassing to Democrats. Podesta is known for his art collection: he and his former wife, Heather, owned Shepard Fairey’s famous “Hope” portrait of Barack Obama, which they donated to the National Portrait Gallery.

NBC News reported last week that Podesta, who served as an aide to the late Senator Ted Kennedy before opening a lobbying firm in 1988, was being investigated for possibly violating US rules that force lobbyists to disclose work for foreign governments.

Mueller was investigating one of Manafort’s campaigns, the European Centre for a Modern Ukraine, and Podesta’s firm, the Podesta Group, was one of the companies that worked for Manafort, allegedly to improve Ukraine’s image.

Mueller’s investigation is broadly examining claims that the Trump campaign may have colluded with Russia in the 2016 election, but the investigation into Podesta reportedly focuses on whether or not Podesta properly alerted authorities to his work for the Ukraine group.