Speaking to Inside Soap, the Darren Osborne actor claims the pair - who play middle-aged married couple Jack and Frankie - kissed for 10 minutes as he deliberately missed his cue.
"Jimmy and Helen had to do a scene on a waterbed where Nancy and Darren catch them at it," he recalled.
"They had to keep kissing until I said my line, so I just let them go for it for 10 minutes and taped them on my phone!
"The crew were all in on it and it was really funny - but Jimmy and Helen were a bit embarrassed."
Meanwhile, Dawson outlined an ambitious desire for Batman star Tom Hardy to play a cousin of alter ego Darren.
The 30-year-old added: "I'd like Tom Hardy to come in and be Darren's second cousin, just so we could have a right blast together on set."
Dawson was earlier this month nominated alongside Jessica Fox, who plays lover Nancy, for the 'Best On-Screen Partnership' category in this year's British Soap Awards.
> Read Digital Spy's recent interview with Ashley Taylor Dawson