An English language teacher who admitted filming up the skirts of thousands of Melbourne women and girls for seven years has been jailed.

Ricardo Herrera’s dark secret only came undone when staff at a large retail store became suspicious and contacted police, after he visited three days in a row in August, 2016.

The County Court heard Herrera, 37, had followed female staff around the store and carried a bag with an iPhone attached to an empty shoe box, filming under their skirts when they were distracted.

He later told police he had been upskirting since 2009 and knew it was wrong, but didn’t know how to stop.

Videos he shot included children in a playground and a three-year-old child getting changed at a public swimming pool.

A search of his home also uncovered thousands of child pornography images and videos.

Colombian-born Herrera, of Ivanhoe, was jailed on Friday for four years and three months, with a minimum three years.

One of his upskirt victims said she felt emotionally violated.

“I watched back the video and I felt sick,” she said in her statement. “I never in a million years thought someone would violate me in that way.”

County Court Judge Amanda Chambers said Herrera invaded the privacy of women and children in “planned, predatory and sustained” offending.

She said his obsessive and disturbing behaviour left his known victims distressed, disgusted and ashamed.

His involvement in child pornography also helped create a market for the exploitation of vulnerable children, the judge said.

The court heard Herrera felt deep shame about his crimes and wrote a letter of apology to his victims.

It heard the migrant, who worked as an English language teacher, felt isolated in Australia after splitting from his wife and fell into a major depression.

Judge Chambers accepted his remorse was genuine but remained “somewhat guarded” about his rehabilitation prospects.

He was jailed as a serious sex offender and will be deported to Mexico, where he lived before Australia, upon release.

Herrera pleaded guilty to accessing, producing and possessing child pornography and intentionally capturing genital images.

-AAP