Welsh Assembly deputy presiding officer and Labour AM John Marek has been dropped as the party's assembly election candidate for Wrexham.
John Marek will appeal to party executives
Dr Marek had lost the confidence of local party members after being accused of bringing the party into disrepute.
The winner of the reselection process announced on Saturday is Dr Marek's former secretary, Lesley Griffiths, who said she was "extremely happy" about winning the vote, 84-80.
Dr Marek said he now intends to appeal to Labour's Welsh Executive after claiming he was the victim of a smear campaign.
Dr Marek was not automatically selected as a candidate after he was accused of making comments that undermined the Labour party.
He said the campaign was unfair and he highlighted a campaign of "lies and smears" against him.
Dr Marek will now appeal to the Welsh Labour Executive, calling on them to dismiss the result of the vote.
Lesley Griffiths: ' Extremely happy'
And he has called on Mrs Griffiths to withdraw her candidature until the appeal is over. She said she looked forward to the party's executive ratifying her selection.
The Executive will discuss Dr Marek's appeal on Friday evening, following this week's pre-election Welsh Labour conference.
"I am delighted to have been selected - it was a wonderful result," said Mrs Griffiths.
"It was an open, democratic selection that Wrexham Labour Party members wanted.
"I felt that, although I had worked for John for two years, that shouldn't exclude me from putting my name forward for selection," she added.
Dr John Marek
The 250 members of the Labour party in Wrexham heard a five-minute campaign speech from each prospective AM in hustings during Friday and Saturday.
This was followed by a 10-minute question-and-answer session.
The full reselection battle was called after Dr Marek failed to win a vital renomination ballot in December 2002.
John Marek biography:
MP for Wrexham 1983 - 2001
He taught in the Applied Maths Department of Aberystwyth
Labour spokesman on health 1985-87 and Civil Service/Treasury 1987-1992
He is a member of the International Astronomical Union.
He had originally decided to try renomination rather than face a disciplinary hearing, but lost the ballot of local and union branches by 13 votes to 10.
As the sitting AM for Wrexham, Dr Marek was automatically included on the shortlist, which also featured Ted George, the leader of the employer's side in the firefighters pay dispute.
Dr Marek, who has been MP and then AM for Wrexham for nearly 20 years, has a reputation for angering members of the Welsh Labour Party.