Commerce Minister David Clark has rebuffed National's offer of legislation to address concerns tighter credit rules are stopping people from getting mortgages. 

He has written to Nicola Willis and Andrew Bayly, the National MPs who first went to him asking the Government pick up a National bill designed to fix the credit crunch, saying he believes adopting their fix would cause "unnecessary delays". 

Regulations under the Credit Contracts and Consumer Finance Act (CCCFA) have been blamed for people having mortgages turned down over trivial matters like gym memberships and Netflix subscriptions. 

The Government has commissioned a review of the situation, seeking to understand whether the regulations are actually to blame for the credit crunch, or if people are being declined because of other economic factors, like banks becoming more risk-averse as property prices rise, and borrowers not meeting loan-to-value requirements. 

The CCCFA regulations were initially designed to tackle irresponsible lending from loan sharks. National's fix would have allowed the Government to have different sets of regulations: one strict set for loan sharks, and another, more permissive set for banks who would use existing rules to determine risk. 

In his letter, Clark noted that National actually backed the amendment that led to the creation of the new regulations (although National was not involved with the actual regulations themselves). 

Clark's review of the CCCFA will require MBIE to report back in February on possible problems, after which Clark will outline a possible response. 

In light of this, Clark told Willis and Bayly that National's bill would likely slow the process down. 

"I note that if the Government adopted your Bill. It would cause unnecessary delays in dealing with this matter. 

"Your Bill does not detail the regulations that you are proposing which would risk creating uncertainty for the sector. 

"Based on my meetings with the banks last week. I detect little enthusiasm for an entirely new set of regulations for the banks and regulated entities," Clark wrote. 

He wrote that the banks had suggested "small tweaks" that could be made to the legislation to ensure its "purpose" was being met. 

Willis pushed back against Clark's criticism, saying it was effectively an admission that the regulations, which National did not back, were the problem - not the legislation itself, which was the part National backed. 

"The minister now appears to accept that it is his poorly drafted regulations that are causing havoc for New Zealanders trying to get loans," Willis said. 

"We continue to believe a bipartisan effort is warranted," she said. 

Clark doubled down on his suspicion that structural factors might be causing the credit crunch. 

He wrote of a " number of factors at play" in the mortgages, "including Reserve Bank moves on LVR restrictions and changes to the Official Cash Rate, which have had an impact on bank lending". 

Clark also said that "a number" of media reports on people being turned down for loans were "incorrect", and noted that Reserve Bank mortgage data showed first home buyers increasing their share of lending since the regulations came into force. 

The same data shows less lending overall, but that could be because the volume of houses being sold had dropped. 

Willis said it was difficult to have faith in the review that will form the basis for Clark's recommendations, given it is being undertaken by many of the same officials that wrote the regulations in the first place. 

"Until we see his solutions it is difficult to give him a tick and a pass mark, the officials he put in charge of the review of the regulations are the same officials who were in charge of the review in the first place," he said.