Unqualified gasfitters may have been at work in Auckland and Northland for the past three years - prompting a warning that people with new gas fittings in their homes should check the work is safe.
The Plumbers, Gasfitters and Drainlayers Board is investigating an Auckland gasfitter whom it suspects has on-sold legitimate gas certificates for use by rogue labourers.
It began its investigation after a woman complained that she had not been given a compliance certificate for the gasfitting work. To date, 10 suspect jobs have been found and repaired.
Board chairperson Hazel Armstrong says some houses have been identified as having at-risk gas fittings and these are being assessed by Energy Safety.
Consumer New Zealand says it is very concerned at the length of time rogue gasfitters may have been operating, without the governing body being aware.
Hamish Wilson from Consumer says it calls into question the integrity of the system. He says it is very important homeowners get compliance certificates for both gas fitting and electrical work.
The Insurance Council says claims as a result of faulty gasfittings by suspected rogue workmen are likely to be covered.
It says if homeowners genuinely believed the work was carried out by registered people then there would not be a problem with their claim.