Owen Paterson, Conservative MP for North Shropshire, is facing a 30-day suspension from the House of Commons after parliament's standards committee ruled that he had broken lobbying rules on a number of occasions.
Mr Paterson has issued a strong criticism over how the investigation was carried out, and said he is prepared to go to court to clear his name.
But the committee has rejected his claims saying: "Mr Paterson made a number of arguments and allegations about the process followed in this case.
"The committee addressed each of Mr Paterson’s arguments in detail in the report and set out its reasons for rejecting them."
Mr Paterson was found to have repeatedly lobbied ministers and officials on behalf of two companies for which he was acting as a paid consultant - Randox and Lynn's Country Foods - in an "egregious" breach of paid advocacy rules. He also failed to declare his interest as a paid consultant to Lynn's in emails to the Food Standards Agency.
There have been calls from opposition politicians for Mr Paterson to resign but members of his own party have offered their backing, with suggestions that a number could vote against the parliamentary motion required to approve his suspension.
If the motion is approved then Mr Paterson could also face a recall petition, which could lead to a by-election for the North Shropshire seat he has held since 1997 if signed by 10 per cent of registered voters in the constituency.
Several of Mr Paterson's fellow pro-Brexit backbenchers have spoken out to back the former cabinet minister, who yesterday said he would be willing to take his case to the European Court of Human Rights if necessary.
David Davis MP, former Brexit Secretary, offered his support, saying he had concerns over the process of the investigation.
He said: "This system of investigation would not be acceptable for our constituents, as it does not meet the rules of natural justice, or even ACAS rules.
"I note that none of the 17 critical witnesses appear to have been interviewed by the commissioner.
"And of course, there is no appeal process, which I would demand for my constituents."
Mr Paterson continues to be paid £8,333 by Randox for 16 hours work each month and £2,000 for four hours work every other month by Lynn's. This means he receives more than £111,000 a year in consultancy fees on top of his £81,932 salary as an MP.
Commenting on the proposed suspension, Mr Paterson's fellow Tory Shropshire MP Lucy Allan, who represents Telford, said: "No one with respect for justice can condone this."
Speaking to the Telegraph newspaper Sir Graham Brady, the chairman of the 1922 Committee, said the case raised “clear questions about the absence of due process”.
But Councillor Duncan Kerr, who previously stood against Mr Paterson as a Green Party candidate and represents Oswestry South on Shropshire Council, said the MP should step down in the wake of the findings.
He said: "It is a very sad day when the parliamentary standards committee determine that for the last six years our local MP has placed the interests of the companies who employ him above his duties to the people of North Shropshire.
"The result has been a tragedy for him and for faith in democracy. The wisest course of action would be for him to resign rather than face the further ignominy of a recall petition."
Downing Street has said a motion to suspend Mr Paterson will be moved in the Commons.
The Prime Minister's official spokesman said: "A motion will be put to the Commons in due course in line with the usual process.
"We will do it in the normal process in a timely way when the business allows."