Premier Mike Baird has unveiled his second policy back-down in as many days, announcing he will pursue a trial of shark nets across beaches in northern NSW.

The NSW government has resisted introduction of shark nets in favour of high-tech "smart drum lines" – a decision that has led to accusations Mr Baird is overly concerned with shark welfare.

Smart drum lines use GPS technology to alert Department of Primary Industries scientists when a shark is caught.

A decision to deploy 100 drum lines along north coast beaches was announced by Primary Industries Minister Niall Blair two weeks ago after 17-year-old surfer Cooper Allen was attacked off Lighthouse Beach in Ballina by a 3.5m great white shark.