Questions remain about missing evidence and gaps in the Judith Collins investigation.

The inquiry by former High Court Judge Lester Chisholm found no evidence the former Justice Minister was involved in a PR campaign to undermine then-Serious Fraud Office boss Adam Feeley.

Labour dismissed the report as a whitewash, saying the inquiry's narrow focus meant it was "set up to find nothing and found nothing".

But Ms Collins said the investigation had been thorough.

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She handed over her laptop, two iPhones, and an iPad as well as access to her webmail and social media accounts to the inquiry's specialist forensic expert from KPMG.

That expert went through all her messages and emails between mid-2009 and the day after her resignation as a minister on August 30.

But there were gaps. Only some emails from her Parliament account could be accessed, and her old Facebook account was taken down last year and records covering the critical period could not be accessed.

The inquiry was also unable to access full records for Ms Collins' parliamentary phone number and said the records it did obtain showed only a small number of calls from Ms Collins to Mr Slater and none from Mr Slater to Ms Collins - something that was "surprising" given both said they rang each other often.

From the available correspondence, Justice Chisholm confirmed that Ms Collins had discussed Mr Feeley with one of the key figures in the orchestrated attacks, blogger Cameron Slater.

But claims by Mr Slater in an email that Ms Collins had been "gunning" for him were "embellished" and inaccurate.

Prime Minister John Key said today the clear report meant Ms Collins could come back to Cabinet in the future.

"I think she could come back to Cabinet," he told TV One's Breakfast programme.

He later said: "I think there is a pathway potentially for her."