Andrew Bridgen has apologised to the House of Commons for breaching lobbying rules and breaking the MPs' code of conduct following his suspension.
Politicians agreed to suspend the North West Leicestershire MP, after he was found to have displayed a "very cavalier" attitude to the rules in a series of lobbying breaches.
He had been recently stripped of the Tory whip after appearing to compare Covid-19 vaccines to the Holocaust, admitted he "should have been more alert to the rules".
Mr Bridgen's five-day suspension had been agreed in the Commons unopposed on 9 January and started the following day. He had been unable to attend the session.
The backbencher should have told ministers and officials about his relationship with Cheshire-based firm Mere Plantations as he made multiple representations.
The Standards Committee also found Mr Bridgen called into question the integrity of its commissioner Kathryn Stone on the basis of "wholly unsubstantiated and false allegations".
He appealed against the recommendation to suspend him, but Parliament's Independent Expert Panel dismissed it "on all grounds".
Making a personal statement in the Commons on 23 January, Mr Bridgen said: "This place loses reputation when members fail to maintain the highest possible standards.
"I respect the rules and traditions of this place and I accept the ruling of the Standards Committee and the Independent Expert Panel which heard my appeal.
"I therefore apologise to the House for all my breaches of the code of conduct. The committee found that I breached paragraph 12 of the code on paid advocacy and paragraph 14 on registration and declaration of interest. I should have been more alert to the rules.
"The committee also criticised me for a letter I wrote to the former commissioner for standards during my case after she had completed her investigation.
"I accept that this letter was inappropriate and I apologise to the former commissioner Kathryn Stone."