The News of the World reports that fellow Essex star and fiancée Lauren Goodger has now moved out of their shared flat.
An insider said: "Mark is a love rat with no morals. You don't sleep with someone else when you are engaged to be married."
Wright is said to have had the affair during a night out in Liverpool last week.
The source added: "Mark was flirting with a lot of girls. He even tried it on with Oaks star Gemma Merna."
He was later spotted with Porter, who plays Theresa McQueen in the Channel 4 soap. The insider claims that the pair spent the rest of the night together.
"It was clear to see he was making a move on her. As a single girl, she was loving it.
"He was drunk and showing off. During a game of poker, he was touching her hand and she was grabbing his leg.
"They both knew what they wanted and were in the flat for about three hours before leaving separately. It's madness that Jorgie's fallen for his bulls**t. She thinks they have a future but he's used her."
However, Wright hinted that he was in fact still living with Goodger, as he tweeted last night: "On the way home in the spud mobil looking forward 2 bed hurry up @LaurenGoodger u best be in bed b4 me warming it up. (sic)".
Lauren Goodger reportedly split from Wright earlier this week, following claims that he had an affair with ex-lover Lucy Mecklenburgh.