This morning Labour's campaign spokeswoman Annette King said Mr Key should now reveal who that staff member was, "because all the evidence points to [Key's close advisor] Jason Ede".
Illustration / Rod Emmerson
"New Zealanders deserve better. They want answers. Dirty Politics makes it clear that Jason Ede claims to have accessed the website but John Key can't make up his mind who Mr Ede works for," she said.
"Mr Key and National must name the staff member who accessed Labour's website to clear up this matter once and for all."
Revealing the email yesterday, Mr Cunliffe would not name the person he alleged accessed Labour's website, saying "you can draw your own conclusion".
"It's clear from Mr Hager's book, he [Mr Ede] seems to be John Key's main point man on those kind of operations," he added.
Watch: Key responds to Hager book 'Dirty Politics'
However, National hit back yesterday accusing Labour of digging up "old news" in a bid to smear the Government.
"As Mr Hager's claims continue to disintegrate, Mr Cunliffe has tried to help him out, releasing an email which confirms only what the National Party stated openly at the time - that a National IT staffer accessed publicly available information on Labour's website which the Labour Party had not properly secured," said campaign chairman Steven Joyce.
"The National Party was open with the Labour Party, the public, and the media about this back in 2011."