A plan by UKIP to nominate Neil Hamilton to represent the party on the body that oversees the Welsh Assembly is facing opposition from several Labour AMs, BBC Wales has learned.
AMs will vote on the former UKIP group leader becoming an assembly commissioner later.
There are concerns he is unsuitable for the role after he abstained on a vote aimed at tackling inappropriate behaviour in the Senedd.
The UKIP group was asked for comment.
AMs will need to approve the appointment - which replaces Caroline Jones who deposed Mr Hamilton as leader in May - in the Senedd on Wednesday.
Both Labour and Plaid Cymru are having a free vote. A Conservative source said they expect their party group to back the appointment.
It is not clear how many AMs will vote against Mr Hamilton, and whether that opposition will be enough to stop his appointment if Tory and UKIP AMs back him.
But sources believe many in the Labour group will oppose Mr Hamilton, with some abstaining.
Commissioners oversee different aspects of the operation of the assembly - and earn more money than ordinary backbench AMs.
There are four and each party group gets to nominate one. Normally, who does the job is a matter for the parties concerned. It is highly unusual for the choice to be vetoed.
But nominations still have to be confirmed in the Senedd.
Before he lost his job as leader Mr Hamilton abstained on an interim assembly policy aimed at tackling inappropriate behaviour. Most of the assembly had supported it.
Mr Hamilton has said the policy could lead to members facing "surveillance" by "outsiders".
Confirming that she would not vote for the nomination Vikki Howells, Labour AM for Cynon Valley, said: "The dignity and respect policy is fundamental to how the assembly must operate and I cannot countenance supporting someone who has failed to endorse that policy."
Another source said there was a "strong feeling" within the Labour group that Mr Hamilton's abstention on the policy made him unsuitable given he would be involved in upholding it.
At least one Plaid AM expected to vote against the appointment but BBC Wales has heard that another AM in the party feels uncomfortable about breaking the precedent on commission appointments.
A source said there had been similar concerns within Labour, prior to the offering of a free vote.
One Welsh Conservative said they thought it was "irregular to try and tell a group who they can and can't put forward".
If Mr Hamilton is successful in his bid to be an assembly commissioner he will gain an extra £13,578 on top of his £65,847 basic backbench AMs' salary, bringing his total pay to £80,425.
He had earned £85,000 a year as leader.
One of the commissioners is Joyce Watson - a Labour AM who has been the target of criticism of Mr Hamilton over her description of UKIP AMs as "rabid dogs" in a debate a year ago.
Speaking in May, and before the nomination was tabled, Ms Jones told BBC Wales that David Rowlands was originally asked to do the job, but "gave way" to Neil Hamilton because he "so enjoyed" his role as chairman of the petitions committee.