Only half the required workforce is available for installing ultra fast broadband (UFB), a telecommunications forum has been told.
The broadband scheme is a flagship programme for the government, which says faster internet speeds will help the economy.
The government wants 99 percent of New Zealand homes to be able to get peak speeds of 50 megabits per second by 2025.
But Chorus chief executive Mark Ratcliffe said getting that sort of speed was being slowed because not enough skilled workers were available to install the fibre.
"We don't have enough technical resources to meet the work that is coming through," he told the forum.
"We would need twice the number of technicians that we have got working by the middle of the year."
Other speakers at the forum attributed this problem to the very success of the fibre programme, which had soared ahead of similar ventures in many other countries.
Spark chief executive Simon Moutter said it had taken 100 years to roll out a copper network and it was ambitious to do fibre in six.
Vodafone chief executive Russell Stanners told the forum would-be fibre customers might just have to be patient and wait for their turn to come around.
"In fact as an industry we will have to educate people that it is not the world we used to have where we just turned things on with a computer.
"We are physically having to go out to homes to change things."
Mr Ratcliffe told the forum it took up to six months to train a technician to install fibre, and the work was not easy.
"This is a construction job on every single premise in New Zealand," he said.
"It is not somebody sitting behind a keyboard flicking some switches to activate some services.
"It is a reasonable complicated job. You have to deal with vectoring into a network and connecting into people's living rooms. You have to have a fairly sophisticated person who goes and does that."
Mr Ratcliff said the demand for the installation of fibre was a record in January and looked like being so again this February.
The UFB initiative is a joint venture between the government and four ICT companies.