AN 18-year-old man who conspired with two teenage children of a prominent Sydney barrister to extort $15,000 from a wealthy north shore mother using pornographic photos says he is ''extremely sorry'' and will ''accept his penalty''.

Kyung (Kevin) Hoon Lee, of South Turramurra, faces up to 14 years in jail after he pleaded guilty to delivering the extortion letter to the victim's $4 million Hunters Hill home on May 29.

''Extremely sorry'' ... Kyung (Kevin) Hoon Lee leaves Ryde Court after pleading guilty to a planned $15,000 blackmail attempt. Credit:Domino Postiglione

The woman was told to leave $15,000 in a toilet cistern in the Hunters Hill Hotel or 2000 prints of the ''disturbing photos'' would be released ''to your neighbours, your family, your community and the peers of your children, including school teachers''.

Lee appeared in Ryde Local Court yesterday while the 15-year-old girl and her 17-year-old brother will appear in Hornsby Children's Court today.