A 73-year-old grandfather was allegedly punched in the head repeatedly by an electricity salesman after he denied his sales pitch.

Bob Ikin answered the door of his south-east Melbourne home around 6.30pm on Wednesday and was approached by a door-to-door salesman asking him to change power providers, according to Channel Seven.

But when Mr Ikin rejected the man's proposal, he allegedly became aggressive and hit Mr Ikin, knocking him to the ground.

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Bob Ikin (pictured), a 73-year-old grandfather, was allegedly punched in the head repeatedly by a door-to-door electricity salesman on Wednesday night at his Melbourne home after he denied his sales pitch

'I said but I'm not interested in changing thank you very much, go away,' Mr Ikin said.

'He said 'do you want to make something of it?''

Mr Ikin said after getting to his feet after he was punched in the face, the salesman allegedly punched him again, causing him to fall and hit the back of his head.

He hit his head again after a third punch sent him flying, Mr Ikin said.

Mr Ikin has a black eye, bruises to the back of his head and cuts (pictured)

The grandfather has a large black eye, bruises on the back of his head and cuts.

Mr Ikin's wife told Seven News that she would like to 'return the favour' to the salesman – who has not been identified.

The man is described as between 25 and 35 years old, caucasian and about 185cm tall.

He was wearing dark clothing and carrying a laptop bag over his shoulder.

Police are asking for anyone with information to call police.