New Zealand could be seeing the biggest spike in industrial action in decades

The picket line continues to grow, with nurses, midwives, teachers, court staff and bus drivers among those calling for higher pay.

Victoria University labour expert, Stephen Blumenfeld, says a number of collective agreements have come up for renegotiation in the past few months.

He says it can't be blamed on the Government, but it could be one of the busiest periods of industrial activity in 30 years.

Midwives around the county are holding a series of rolling strikes from today.