Police have confirmed their decision not to lay charges over the CTV building in Christchurch despite "significant" design deficiencies.

Police said this afternoon that they and the Crown Law had reviewed a statement issued by Professor Maan Alkaisi, on behalf of the CTV families, earlier this month about a decision not to bring a prosecution regarding its collapse during the 2011 earthquake.

"The decision not to prosecute was made by police after considering the advice of the Christchurch Crown Solicitor and the Deputy Solicitor-General and meeting with them to discuss that advice,'' a statement said.

Police said they stood by their view that the decision not to prosecute was correct when all the relevant evidence and opinions were taken into account.

Professor Alkaisi said on behalf of the families that the Deputy Solicitor-General did not appear to be aware of all the relevant facts regarding the decision and emphasised that there had been opportunities to rectify design problems in the building, but which the families believed the Deputy Solicitor-General was not aware of.

Both of these matters were expressly considered by the Crown Solicitor in his report and the Deputy Solicitor-General in his peer review,'' police said.

"Those matters were also addressed in the Canterbury Earthquake Royal Commission report, the Beca report and the police report - all of which were considered as part of the investigation and decision making process.''

The statement acknowledged that police did "fully agree'' that there were significant deficiencies in the building's design. Those deficiencies were all noted as part of the initial police investigation and by the Royal Commission and was also considered by expert opinions sought at the time.

"However the Deputy Solicitor-General and ultimately the Crown Solicitor and Police considered the evidential test was not met.

"Police concluded, and remain satisfied, that there was no reasonable prospect of obtaining a conviction in this case."

Police also acknowledged it had been a difficult time for the families of those killed.

"We have tried to be as open and transparent as we can in publishing information to assist in their understanding of the complex, technical issues involved.''