Former Ministers who have defected to New Zealand First say they did not leave their parties - their parties left them.

A slew of high-profile former politicians have joined NZ First as its popularity climbs.

"Granddad was blue, dad was blue, I was blue until I woke up," a New Zealand First member who previously supported National told RNZ on Saturday.

Former Ministers who have defected to New Zealand First say they did not leave their parties - their parties left them.