In the photo, Jack, who has starred in Coronation Street for 15 years, appeared to be urinating on the sign of rival soap, Emmerdale.
Despite some followers being amused, plenty of Emmerdale fans were left royally p’d off - and Jack P Shepherd quickly realised he’d made a mistake.
He quickly deleted the photo from his Twitter feed in the early hours of the morning.
A soap source told The Sun: “Jack had a few drinks like the rest of the Corrie cast, but as the night went on he got a bit boisterous.
“He thought it would be funny to pose for this snap and posted it online, but took it down within seconds.
“Jack knew this could get him in trouble. There’s a big rivalry between the soaps but the ITV bosses don’t want any headaches over rows.”
They added: “Jack’s been in trouble before as well and they’ve all been warned about how they use social media.”
They aren’t wrong on that front; following the Manchester Dogs’ Home fire which claimed the lives of at least 43 animals, Jack sparked outrage with an inappropriate tweet.
He posted at the time: “I have a million ‘hot dog’ jokes.”
After a backlash from fans, the actor made a public apology.
He wrote: “I sincerely apologise for any offence I have caused. This was not intended to be a malicious tweet and I didn’t consider the offence it would cause.
“At the time I didn’t realise the scale of the tragedy but that doesn’t excuse my behaviour. I now realise how insensitive I have been. I have made a donation to the MCR dogs home and I’m very sorry for my behaviour.”