During the episode, Matt had a tense exchange with Mark as he brought the timber into the house.
Matt questioned how he was able to get the materials for the next room there so quickly.
"When did you order that?" asked Matt, to which Mark replied with "Magic … yesterday."
Amazed, Matt continued to probe Mark.
"We were allowed to do that?"
“Yeah … no-one said we couldn’t," Mark said.
Matt didn't seem convinced.
"Well I thought we weren’t allowed to work ahead," he said.
An annoyed Matt continued to complain about the crafty duo in an interview with his wife El’ise, accusing Mitch and Mark of breaking the rules.
"It’s not right, you can’t just be working ahead, it should be an even playing field for everyone," Matt said.
Matt's attitude seemed contradictory to his original views on dealing with competition.
Prior to beginning The Block, Matt told WHO that he and El'ise "don’t necessarily stress about what everyone else is doing and go in that kind of competition – it’s more against ourselves to make sure we’ve got the perfect room."
However, in Monday night's episode, Matt seemed to be fixated on what his competitors were doing.
"It’s a massive leg-up, huge leg-up. I thought that’s cheating, you’re bloody cheating, you can’t just ring ahead and think this is fair," he said.
To Matt's dismay, host Scott Cam said Mitch and Mark had “kept it all above board” and hadn’t cheated — something Mark adamantly denied as well.
"We hadn’t started any work, we spoke with our builder and assessed what we thought would be the next room," he said.
"And (we) knew that if we waited until Monday we wouldn’t get materials until Tuesday, so we ordered early."
WATCH: Meet The Block's Mitch and Mark
Eventually, Matt let it go.
"If they took the gamble and placed an order and it wasn’t that room maybe it would have backfired on them," he said. "But good luck to them, they’re in front, so we’ll see what happens."
The Block continues Tuesday 7.30pm on Channel 9