In scenes that were aired before 10pm last night, the couple were seen getting so hot and heavy that viewers were left questioning whether they had even had sex.
Bizarrely, in tonight's episode, Laura will be seen insisting that she and Marco are just friends - as apparently she "just likes kissing"....
Following last night's on-screen antics, which showed some very explicit behaviour, hundreds of disgusted viewers complained to television watchdog Ofcom.
An Ofcom spokesman told Mail Online: "We will assess these complaints before deciding whether to investigate or not."
A BB spokesperson has declined to comment.
Marco's fashion designer fiancée Kim Melville-Smith, meanwhile, has denied they are "in an open relationship", after it was claimed she gave him a "hall pass" before entering the show.
Ahead of tonight's episode, which will show Marco daring Laura to remove her bikini top in a game of hot tub truth or dare, Kim has retweeted a poll she was forwarded by her sister. The poll asks: "If you were Marco's fiancée what would you do?" The highest rated answer is: "Cut his balls off."
Sharing it with her followers, along with four crying with laughter emojis, she said: "I was sent this by my sister... #bbuk #bbmarco."
Following last night's explicit scenes, Kim had posted this in a series of now-deleted tweets: "FYI I said #hallpass NOT open relationship. I don't watch BB, but I heard this today. Worst thing I can't even talk to him #bbuk #bbmarco."
Big Brother continues tonight, 9pm, Channel 5