Conservative MP Nadine Dorries has apologised to MPs for failing to properly register income made from her appearance on I'm A Celebrity in 2012.
Ms Dorries said the breach of the rules had been "inadvertent" but she owed MPs a "full and unreserved apology".
She cited a confidentiality clause and the fact the fees were paid to a firm of which she was a shareholder for not declaring the outside earnings.
But the standards committee said she must apologise.
The standards commissioner also criticised the MP for Mid-Bedfordshire for not co-operating with their inquiry, saying this amounted to a "serious breach" of the MPs' code of conduct.
However, it said it believed that the MP's failure to register her financial interest as a shareholder in the Averbrook media consultancy until June 2013 was "inadvertent" rather than deliberate.
The standards committee of MPs, which has the power to sanction members in light of the commissioner's findings, said the MP should make a "personal statement" to the House to apologise.
The MP lost the Conservative whip when she appeared on I'm A Celebrity in 2012 but Ms Dorries said she succeeded in communicating her views to a wider audience and her constituents had continued to be represented while she was in Australia, where the show is filmed.
The issue of Ms Dorries' income from TV appearances, including the ITV show, was referred to the watchdog earlier this year following a complaint by Labour MP John Mann.
The watchdog found she had not recorded details of eight separate media appearances on six different programmes in the register of MPs financial interests.
If the MP had been paid for any of these appearances, the watchdog said it would represent a breach of the rules - requiring MPs to disclose time spent on their outside employment and the amount of money they make.
"The omissions from Ms Dorries' entry means that constituents, other members and the wider public do not have access to this information in her case," the commissioner said. "The omissions also have the potential to undermine public confidence in the completeness and accuracy of the register."
In a letter to the committee last month, the MP said she "unequivocally never sought to impede" the inquiry in any way.
"In respect of both the code and guidance there is unfortunately an ambiguity, which fails to make clear to members their responsibilities in terms of the declaration of outside interests and contractual obligations," she added.
Ms Dorries updated her entry on the register in October. It showed Averbrook's turnover for the previous year was £142,000, yielding a profit of £82,000. It also showed Ms Dorries took a £10,000 dividend at the end of the month.
Ms Dorries told the standards committee that if she disclosed how much she had been paid by ITV she would "fall foul" of the contract's confidentiality clause but the MPs said requirements to provide information to Parliament "overrode" confidentiality agreements.
The MPs said the disciplinary system in the Commons "depended on members being prepared to explain their conduct, to submit to public scrutiny and where necessary, to respond to the commissioner's inquiries".
"We recommend that Ms Dorries register all payments in respect of her employment, whether or not they have been channelled through Averbrook or any other third party and apologise to the House by way of a personal statement."
It also said the MP should seek advice from officials about her entries in the register before the end of the month and her future compliance with the rules would be monitored.
The MP had the whip restored in May and was recently re-adopted as the Conservative candidate to fight the next general election in her constituency.