New Zealand’s Justice Minister Judith Collins has quit as a minister amid a scandal about her ties to a controversial blogger.

The under-fire senior National MP quit on Saturday after Prime Minister John Key’s office was given a copy of an email that suggests she may have involved in discussions with Whale Oil blogger Cameron Slater in 2011 about undermining the then director of the Serious Fraud Office Adam Feeley.

Ms Collins was the minister responsible for the SFO at the time.

“The prime minister and the National Party have an election to win and I wish to stop being the subject of daily distractions,” Ms Collins told a press conference in Auckland.

“I have been the subject of a two-year smear campaign and it seems that every day both I and the prime minister are having to defend me against false allegations and innuendos.”

Ms Collins denies any allegations she was trying to remove Mr Feeley from his position.

“I completely refute any such inference,” she said.

“I cannot control what other people say about me or when they leverage off my name.”

Ms Collins has asked for an inquiry and says she will co-operate fully.

“I look forward to clearing my name. I will not let this disappointment define me.”

Mr Key says his office was given a copy of the email – between Slater and others, but not Ms Collins – in confidence on Friday and he spoke to Ms Collins on Saturday morning.

Asked if he would have sacked Ms Collins if she hadn’t offered to resign, Mr Key said the email indicates a matter of a very serious nature.

“I think the only option would have been for the minister to resign, but in the end, she could see the seriousness of it.”

The new allegations were far more serious than previous allegations levelled against Ms Collins, Mr Key said.

“This is a far more serious matter than anything else I’ve seen.”

Ms Collins shouldn’t expect to return to cabinet if National was re-elected, Mr Key said.

However, he didn’t rule out Ms Collins returning as a minister in the future.

Ms Collins’ resignation takes effect immediately.

She will continue campaigning to be re-elected as the MP for Papakura.