The leaking of a recording of a shadow cabinet member criticising Jeremy Corbyn was a "ghastly smear" against the Labour Party, according to Dr Adrian Heald.
The Labour candidate for Mid-Norfolk said everyone was entitled to a private conversation, and it was "unpleasant" that the audio had been shared publicly.
In the recording, leaked to the political blog Guido Fawkes yesterday, shadow health secretary Jonathan Ashworth can be heard saying that he did not believe the Labour Party would win the election, and that Mr Corbyn could pose a security risk if he entered Number 10.
Mr Ashworth has since dismissed his remarks, recorded secretly by his friend and Tory activist Greig Baker, as "banter".
Speaking to talkRADIO, Dr Heald said: "We don't know what was said in terms of what prompts were given to Jonathan in terms of the comments that he made.
Mr Ashworth apologised for his remarks
"It has been a perfect example of the kind of horrible, ghastly smear campaign that has been put against the Labour Party throughout this campaign."
Responding to the recording, the Labour leader dismissed it as "banter between two old friends", and insisted Mr Ashworth had his "full support".
He added that the shadow cabinet member had an "odd sense of humour".
Dr Heald continued: "This is a private conversation. We all have private conversations and it is completely inappropriate, unpleasant and ghastly that this was leaked to the media.
"I completely support Jeremy. Jonathan has apologised for his comments and said it was only banter and I believe him on that matter."
Dr Heald is standing as an election candidate alongside George Freeman (Conservative Party), P J O`Gorman (Independent) and Steffan Aquarone (Liberal Democrats).
talkRADIO: Your election station - listen live