A man was arrested by a member of the public for allegedly filming up women's skirts in Sydney.

A man who was arrested by a concerned member of the public for allegedly filmed up women's skirts on the Sydney rail network has been charged.

The 51-year-old accused was brought to the attention of police by the member of the public who said he saw the man filming up the skirt of a woman at Town Hall Railway Station Friday morning.

The 'upskirter' is also accused of filming up another woman's skirt on an escalator at Wynyard station a short time later, police said in a statement.

Lawyer Michael Fitzpatrick reportedly saw the dramatic citizen's arrest take place.

"I was just walking up the escalator and, towards the top of the escalator, a man who was in front of me yelled out to another man on the escalator beside us - who was also going up - words to the effect of, 'I saw what you did' or 'Stop filming up that girl's skirt,' " Fitzpatrick is quoted as telling Fairfax .

"The man, I later found out, apparently had his arm outstretched with his camera phone and he was filming up the girl's skirt in front of him as he walked up the escalator."

"The guy kind of just kept a hold on his arm and held onto him and said 'No you're not going anywhere.'"

The 51-year-old accused was later apprehended by police and charged with two counts of film a person's private parts without consent.

He was granted bail to appear at Downing Centre Local Court in February 2017.