Lomas, who was married to Corrie actress Kym Marsh before they separated in October 2013, is said to have approached Matt Barker in a nightclub in Manchester and punched him in the face.
Witnesses at the scene said the personal trainer then tried to retaliate but was stopped by a group of men.
Kym and Jamie
Matt, 24, had a six-week-relationship with Kym after her divorce was finalised in January 2014.
Police confirmed that there had been an assault at the Manchester nightclub - and that they were going to get in touch with the individual involved.
Personal trainer Matt
Kym and Jamie were together for five years and have a daughter together, Polly Lomas, who is 3. They both also have children from previous relationships.