Green MP Caroline Lucas is under investigation for alleged violation of House of Commons rules by accusing money of a round of Parliament.
The Brighton Pavilion representative said on Wednesday that he “did not believe” that he had done something wrong after the inquiry by the Parliamentary Commissioner for Standards came to light.
An online fundraiser from his local party ahead of the December general election offered a 30-minute tour led by Ms Lucas and put her value at £ 150.
Lucas said in a note: “I am aware that a case against me has been presented to the Commissioner and an investigation is currently underway.
“I don’t think I did something wrong.
“I have been informed that the commissioner’s investigations are confidential, so it would not be appropriate for me to say anything else at the moment.”
The local Lucas newspaper reported that 69-year-old Hove resident Stuart Bower complained to the commissioner about the crowdfunding page saying it was “unethical”.
“Charging a tax and increasing your income to get people around the House of Commons is making the office discredit,” he added.
Kathryn Stone, Parliamentary Commissioner for Standards, wrote again saying she was not launching an investigation into her complaint because “an overlapping issue is already under investigation,” Argus said.
Ms Stone’s office did not confirm or deny that the investigation had been initiated.
Guided tours of Parliament can be booked online for £ 26.50 for adults, but UK residents can arrange free visits by contacting their constituency.