Eamonn Holmes has sparked over 400 complaints with comments he made about 5G technology and coronavirus, which TV watchdog Ofcom says it will assess as a "priority".
This Morning's co-presenter, 60, was criticised by scientists and viewers for remarks he made on the ITV show.
An Ofcom spokeswoman said it had received 419 complaints and told the PA news agency: "We are assessing this programme in full as a priority."
Holmes, 60, weighed in on the ITV show after presenter Alice Beer branded the conspiracy theories "ridiculous" and "incredibly stupid".
The broadcaster who was co-presenting with wife Ruth Langsford, responded that "it's very easy to say it is not true because it suits the state narrative".
He told Beer: "I totally agree with everything you are saying but what I don't accept is mainstream media immediately slapping that down as not true when they don't know it's not true.
"No-one should attack or damage or do anything like that but it's very easy to say it is not true because it suits the state narrative."
The presenter added: "That's all I would say, as someone with an inquiring mind."
So I've just heard #ThisMorning presenter Eammon Holmes legitimise the stories linking the Coronavirus lockdown to 5G. On national television. Wow. How irresponsible can you get. Switching off. Hope Holly & Phil are back soon.
— vickster51 (@vickster51) April 13, 2020
Experts have previously dismissed any link, calling it a "physical and biological impossibility" and branding "conspiracy theorists... a public health danger".
Scientists criticised the presenter for his comments.
Prof Brendan Wren, professor of microbial pathogenesis at the London School of Hygiene & Tropical Medicine, said: "I welcome enquiring minds, but this needs to be based on some fact and not pedalled as a conspiracy as this causes untold damage."
— Johnson McJohnson (@jimmyma42227225) April 13, 2020
Dr Michael Head, senior research fellow in global health at the University of Southampton, said: "The world of infectious disease experts, covering a wide range of disciplines, backgrounds, countries and employers are united in that we know how transmission of a virus works.
"Holmes is not known for his scientific expertise and appears to have very little in the way of relevant qualifications, experience or any kind of written track record in peer-reviewed journals."
Dr Simon Clarke, associate professor in cellular microbiology at the University of Reading, said that the idea that Covid-19 is caused by 5G mobile signals is "complete rubbish".
Viewers also criticised the presenter's comments and accused him of "legitimising" the conspiracy theories.
#thismorning well done Eamonn. You just added more fuel to this 5G conspiracy theory by legitimising what is utter nonsense. You need to research properly before pronouncing
— Andy Green (@EI3HG) April 13, 2020
After the programme was broadcast, Holmes defended his on-air comments by saying that he "didn't spread" the conspiracy theory.
"I reserve the right to listen and question," he added.
It comes after MPs called for social media companies to be held to account following reports of phone masts being attacked after theories spread online.
A Government spokesman said: "We are aware of a number of attacks on phone masts and abuse of telecoms engineers apparently inspired by crackpot conspiracy theories circulating online.
"Those responsible for these criminal acts will face the full force of the law."
Ofcom is also assessing comments made by David Icke about coronavirus.
And the media watchdog previously ruled that a local radio station had breached its rules after one of its guests suggested the Covid-19 outbreak was caused by the rollout of 5G mobile technology.
ITV has been approached for comment.