The company that holds the main contract for repairing earthquake-damaged homes in Christchurch says it monitors all work very carefully to avoid fraudulent behaviour.
Fletchers says after discovering four false invoices, it referred them to the Earthquake Commission (EQC) and sacked the contractors responsible.
New Zealand First says fraudulent activity is rampant in Christchurch and has accused Fletchers of signing off on false invoices.
But the unit running the project, Fletcher Earthquake Recovery, says it takes the taxpayer-funded contract very seriously and has a robust audit process.
General manager David Peterson says four fraudulent invoices have been discovered and the company checks each job to make sure the work has been done.
"The contractor is brought in. We go back and have a look through the property to make sure that has, in fact, been the case.
"The contractor is either asked to remedy that work or, if it's deliberately fraudulent, we then carry out an investigation, operate a strike system for the contractor and then pass that result investigation back to the Earthquake Commission."
Mr Peterson says Fletcher Earthquake Recovery refers cases of fraud to other enforcement agencies.
New Zealand First leader Winston Peters said he is getting a steady stream of information about work that has been paid for, but not completed.
"Fletchers gets a massive amount of taxpayers' money as the project leader. They scope out the costs contract by contract, and they sign out the invoice. They are making a packet on false, fraudulent claims - they know it."
The Serious Fraud Office says it is conducting two quake-related fraud investigations in Christchurch. They involve the EQC and private insurers, and relate to services for repairs.