The incident happened after Mr Richardson, 24, and Ms Ellison left a fashion show at the Place nightspot in Victoria Street.
After getting into Ms Ellison's Range Rover, the pair watched in terror as a van blocked their way before four masked men surrounded them and began to attack their vehicle. One had a machete and another a baseball bat.
The man with the machete smashed the passenger window and struck Mr Richardson across the stomach.
Ms Ellison then managed to start her car and the couple escaped.
Police say they are investigating the incident which happened at 11.30pm last Thursday.
A spokesman for The Place said: "Jennifer and Tony enjoyed a wonderful night at the fashion show.
"There were no incidents of any kind inside the bar itself and we were unaware of anything having happened to them after they left."
The latest incident comes just months after Ms Ellison's luxury home in West Derby was raked with gunfire.