Sixteen Christchurch rebuild companies have breached employment laws and owe staff more than $236,000, an audit has found.
The Ministry of Business, Innovation and Employment discovered the breaches through audits.
The audits are part of a joint programme with Immigration New Zealand and WorkSafe New Zealand to ensure that labour standards were adhered to during the rebuild of the earthquake-hit city.
The audit programme follows an increasing number of complaints about the employment practices of some businesses associated with the reconstruction of parts of Christchurch.
Many of the breaches relate to incomplete employment agreements, unlawful deductions from wages and insufficient records.
Nine improvement notices and six enforceable undertakings have been issued, and one case has been referred to the Employment Relations Authority.
Southern region manager Steve Watson said those commissioning work and head contractors must take responsibility for monitoring compliance.
Its audits had found workers were owed $236,000 - money they were not aware they were owed it.
Listen to Steve Watson
"The most significant breaches, and the most serious ones in my view, are the ones where there's a total failure to keep wage and time records, or the wage and time records kept are significantly poor," Mr Watson said.
"Without those records, it's impossible, or very difficult, for us to identify how much people are being paid, how many hours they're working and whether, in fact, they're being paid at the minimum wage or getting their holiday entitlements."
The investigation had revealed a disappointing level of non-compliance and action was being taken, he said.
"It's a serious issue and one that we're addressing through our enforcement action by issuing a number of improvement notices and enforceable undertakings."
Workers were not aware of their rights in most cases, he said.
Forty Canterbury companies have been audited, with 23 completed.