A 19-year-old man who pleaded guilty to blackmailing a woman he met on a social networking site has escaped a prison sentence.

Samuel Mark Nicholls was sentenced to 12 months supervision and 200 hours of community work in the High Court in Nelson on Wednesday.

Nicholls met the woman on the social networking site Bebo in 2010 and they exchanged cellphone numbers.

They communicated via the internet and text messages, and at some point Nicholls asked the woman to send him naked pictures of herself.

In August 2011, Nicholls, who was 18 at the time, sent the woman a series of text messages asking her to come over to his house.

When the woman refused, Nicholls told her he would send the naked photos he had of her and they would be "everywhere".

He subsequently told her he would delete the photos if she had sex with him.

The woman then complained to police.

Justice Jill Mallon said in her sentencing remarks that blackmail usually, but not always, carries a prison sentence.

However, she said that while Nicholls' threats were upsetting to the woman, they had not caused any lasting impact.