The allegations came to light earlier this week when co-star Cyrell Paule revealed that Heidi had told her, while they were filming Married at First Sight Australia, that Mike had slept with another girl.
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19) Matthew Bennett
Instagram: @mattybgratefulFollowers: 76,439Earnings per post: £365
Speaking to The Sun about the matter, the 31 year old said, " When he was talking to the guys and saying, 'Oh it just didn't work out, but she's a lovely girl', I thought, 'Don't talk out of your f---ing arse, you lying piece of s---, you were f---ing another b---h while you were filming.'"
Responding to the claims, Mike told the publication that they were "simply false" but didn't elaborate.
The pair came to blows recently after Cyrell refused to feature on Mike's podcast. Following the rejection, Mike, 45, swiftly blocked the mum of one (to Boston, one) on Instagram and at the grand reunion (which is yet to air in the UK), their feud apparently came to a head.
Commenting on the whole affair, Cyrell told the publication, "I don't even listen to podcast so why the f--- would I want to go on it.
"It never gets aired, but I said [at the grand reunion], 'Why are you saying hello when you unfriended me on Instagram? You don't unfriend me then talk to me.'
"He then hated me even more."
Now, three months after the reunion was filmed, Cyrell has admitted that she doesn't care if Mike hates her.
She said, "It's no loss to me that Mike Gunner, some bald ass dude that wants to look like Jason Statham stops talking to me."
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Mike isn't the only MAFS star that Cyrell's fallen out with and recently she accused cast mate Martha Kalifatidis of lying.
Yep, when Martha - who famously chucked a glass of wine over Cyrell's head - shared an Instagram Story to try and let bygones be bygones, Cyrell hit back, claiming that the 32 year old was merely posting on social media in a bid to gain followers.
She wrote, "Though I appreciate everyone trying to convince me that Martha is being kind and showing herself in a different light, there has been words said to me that I will never forget. Being referred to as an animal raised in a zoo is one of them."
She continued, "Please DO NOT use me as a way for people to like you. A sincere apology goes a long way. Not an Instagram post for the world to view! And for your benefit."