There are concerns that industrial action may escalate as a result of new law being pushed through from the Labour-led government.
Under current law if you take partial strike action you can get a partial wage docking for that, but that's set to change.
EY employment law leader Christie Hall told Mike Hosking if that law does change, longer strikes could occur.
"You will have people taking partial strike action and an employer who's response is to lock them out, which will escalate things quite considerably, or you will have people saying 'well, there's no point taking partial strike action if I'm going to be locked out, I may as well go for a full strike'."
More than 200 workers at Lyttelton Port are currently on strike over a pay dispute with the port company.
They will today protest outside of Christchurch City Council, whose commercial arm, Christchurch City Holdings, has full ownership of Lyttelton Port Company.
Rail and Maritime Union organiser John Kerr will present a letter to the chair of the Holdings board at midday.
The National Party is concerned at the growing number of strikes under the Labour-led government.
Spokesperson for Workplace Relations and Safety Michael Woodhouse says the unions are effectively holding the government to ransom.
"I think what we're seeing is a confidence in the unions that they are going to get what they want if they push their weight around. I think that's a shame."
He says there is a clear correlation between the election of a Labour-led government and the increase of union-led industrial action, and Woodhouse says this is just the beginning.
"This is the first of a series of industrial actions I think we will see from public sector unions, for example where we see the nurse's unions and the teachers unions setting themselves up with very high expectations for pay growth."
LISTEN TO CHRISTIE HALL TALK WITH MIKE HOSKING ABOVE