
Foreign Secretary Yvette Cooper said the by-election "shouldn't be happening" while Conservative leader Kemi Badenoch said her party would not participate in "the fake election, which Nigel Farage is causing to distract people from what is happening".
The Lib Dems have called on the government to block Farage's resignation until the standards investigation had concluded.
Speaking about other parties refusing to stand against the Reform UK leader, Offord said Farage was the victim of an "establishment stitch up".
He told BBC Radio Scotland Breakfast: "He is anti-establishment, he's anti the incumbent parties, and he's been a thorn in their side for 25 years.
"This is an opportunity for them to knock him out the ring, and they're feart (sic)."
Offord said he did not know the full circumstances of the financial support gifted to Farage but insisted that the Reform UK leader had done nothing wrong.
He said the £5m gift had been given on an unconditional basis when Farage was not "even thinking of standing to be an MP" but that he later changed his mind.
Asked about Cottrell's support, Offord described Farage as an "international figure" who meets "interesting people along the way".
He said Cottrell was a "personal friend" of the Reform leader.
He added: "Right now, there's a narrative that if anyone's made any money, they're a bad person, and this is really bad for Britain."
Labour, the Conservatives, the Liberal Democrats, the Green Party and Restore Britain have all ruled out contesting the Clacton by-election.
Farage will face competition from Count Binface - the pseudonym of comedian Jon Harvey, who regularly takes part in high-profile ballots.
The probe, which started in May, has been paused following Farage's resignation but it could be resumed if he wins the by-election and returns to Parliament.
One possible outcome of the investigation is a suspension for Farage, which could lead to another by-election.
Polling expert Professor Sir John Curtice predicted that the forthcoming Clacton by-election could turn out to be a "damp squib" after other major parties said they will not contest the vote.
However, he said the move would get Farage "back in the headlines".
He added: "Reform are still ahead in the opinion polls, but with the slight boost for Labour in the wake of the resignation of Keir Starmer, and the fact that support for Reform has been edging down slowly.
"He would be hoping that the publicity will help to push him up."



