CCTV of the incident at a shopping mall in Livingston, West Lothian, was shown at Livingston Sheriff Court.
Emil Lichota, a Polish national is clearly seen poking the woman’s bottom twice with his finger.
After the second prod she is seen turning round and slapping him hard with her hand.
Lichota, 25, of The Avenue, Whitburn, West Lothian, had been due to stand trial for sexual assault.
He had denied brushing the woman’s neck, seizing her bottom and repeatedly touching and squeezing her buttock.
But following discussions yesterday, he pled guilty to a lesser charge of simple assault and had sentence deferred for reports.
The incident happened at The Mall, in the Craigshill area of Livingston, on March 4 this year. Lichota was told to return to court to be sentenced on December 17.
The Mall is one of Livingston’s largest shopping centres and welcomes thousands of customers each year.