Montana congressman Greg Gianforte was sworn in on Wednesday, just days after pleading guilty to the assault of Guardian reporter Ben Jacobs on the eve of his election.

Gianforte, a software entrepreneur, won a closely fought special House election in Montana last month, assuming the seat vacated by Ryan Zinke after he was appointed president Donald Trump’s secretary of the interior. He has already filed for re-election in 2018.

Before hundreds of members of Congress, with his wife, and two of his four children watching from the gallery, Gianforte on Wednesday raised his right hand and took the oath office.

“Congratulations, you are now a member of the 115th Congress,” House Speaker Paul Ryan said, as the members applauded.

House majority leader Kevin McCarthy, of California, then rose to welcome the to newest member of Congress, who called a “family man” and a “businessman”.

“Now, Montana may only send one member to this body,” McCarthy said, “but out west, it’s not about how many you are, it’s about how much you do. Greg is a doer. And we’re happy to have him here.”

Gianforte rose to address the House for the first time as his wife, Susan, and two of his four adult children, watched from the gallery.

Gianforte said he was “humbled and honored” to have been elected and pledged that his loyalty lies with the people of Montana before the Republican party. “I’m a business guy and an electrical engineer. I’m trained to solve hard problems – not to argue about them, just to get things done,” Gianforte said.

As his first act, Gianforte endorsed legislation that would prohibit lawmakers from earning a paycheck until they passed a budget, impose term limits and ban members of Congress from lobbying after leaving office.

“I am Montana’s lone voice here in this House, sent by the people to do the work of the people,” he said.

Last week, Gianforte was sentenced to community service, a $385 fine and 20 hours of sessions for anger management after pleading guilty to misdemeanor assault.

Gianforte was charged with assault hours after he attacked Jacobs on the eve of the 25 May special election.

Jacobs, who was covering the Montana race, approached Gianforte at his campaign headquarters in Bozeman to ask a question about the Republican healthcare bill. Gianforte responded by grabbing Jacobs, throwing him to the ground and breaking his glasses.

Jacobs captured audio of the encounter. His account was corroborated by a team of Fox News reporters who were in the room.

Prior to sentencing, Gianforte reached a settlement with Jacobs in which the Republican apologised to the reporter and agreed to pay $50,000 to the Committee to Protect Journalists.

In a statement on Wednesday, Jacobs welcomed the Congressman to Capitol Hill. “I welcome Congressman Gianforte to Capitol Hill where I’m confident he will live up to his pledge to champion a free press and the first amendment,” Jacobs said in a statement. “In the courtroom last week, he openly offered to do an interview with me when he came to Washington and I look forward to taking him up on that in the coming days.”

Prior to the official ceremony, Gianforte posed for photographs during a ceremonial swearing in Ryan, his family, and Montana’s three most recent former representatives, Zinke, Steve Daines and Dennis Rehberg, all Republicans.

As they waited for Ryan, Gianforte responded to shouted questions about his arrival in Washington. “There’s more humidity than Montana,” Gianforte observed. He added the reception so far has been “positive”.