51-year-old Giles Feltell, was handed a restraining order in March 2019, which stipulated he could not contact the victim, who is in his 70s, or attend his home in Littleport.
However, on 16 October last year, he turned up at the man’s front door and shouted abuse while making offensive gestures.
At about 1.30pm on 20 January, Feltell again returned to the property and repeatedly knocked on the door and made threats.
When the door was eventually opened, Feltell rushed in, grabbed his step-father by the collar and pushed him against the stairs before leaving.
Feltell broke the restraining order twice more in the following three days by again turning up uninvited and banging on the front door of the victim’s home.
Feltell, of Victoria Street, Littleport, was arrested on 25 January and later pleaded guilty to four counts of breaching a restraining order and assault by beating.
He was sentenced to two years and four months in prison at Peterborough Crown Court.
PC Sarah Kelly said: “Feltell is a prolific offender who showed a complete disregard for the restraining order on him.
“The persistent harassment he inflicted on this elderly man was completely unacceptable and I hope he now reflects on his behaviour.
“Tackling abuse and harassment continue to be priorities for us and we will do all we can to keep victims safe.”