The Council of Trade Unions is calling on the Government to help resolve a dispute over workers it believes are being unfairly treated by Telecom changes to infrastructure.
Lines engineers are angry at a new contracting model introduced by the company's subsidiary Chorus, which handles infrastructure.
Workers are being laid off by Transfield and Downer EDI, which are being replaced by new contractor Visionstream.
Engineers say Visionstream wants them to become independent contractors, rather than employees, which would mean considerable set-up costs and no guarantee of regular work.
Telecom lines engineers plan to strike in Auckland, Wellington and Christchurch on Monday over the issue. Telephone, internet and eftpos services are likely to be affected.
CTU president Helen Kelly says lines engineers have the union's support.
Ms Kelly says if workers are forced to adopt Visionstream contracts, they will not be able to carry out long-term maintenance that phone lines require.
"They will be sent out to do short, cheap jobs. A lot of them will not be able to make a living and drop out of the industry.
"This is a very serious national infrastructure issue. We want the Government to get involved (and) we want Telecom to account for itself."
Meanwhile, there is concern that migrant co-workers will not be allowed to become contractors, due to their work permit conditions.
Auckland lines engineer Peter Kelly believes Visionstream will take advantage of these workers by employing them on cheaper wages.
Chorus has not been available for comment.