The DUP has been urged to reconsider charging £50 for people to go to a seminar with the health minister and his colleagues on the health committee.
The party is holding the event on the future of the health service at its annual conference.
Sir Alastair Graham, former chairman of the committee on standards in public life, said it seemed inappropriate.
"It rather implies that you're having a bit of privileged access if you pay this particular fee," he said.
"I would have thought it was inappropriate for the minister to be confusing his party political role with his public duties which is to engage with the public in Northern Ireland about this review of the health service.
"I think it's probably a bit unfortunate the way they've gone about it."
The DUP has said the £50 fee is to cover the additional costs of the seminar.
However, Sir Alastair said: "I cannot believe the DUP has not got sufficient funds to go ahead with the seminar without the £50 fee."
In an advertising leaflet, the DUP describes the seminar as "an excellent opportunity for you or your organisation to make your views known to the minister".
However, other parties have strongly criticised the event.
The interactive 'health workshop' is taking place next Friday as part of the DUP's conference.
As well as the minister, Edwin Poots, other panellists include Hugh McCaughey, chief executive of the South Eastern Health Trust, George O'Neill, chair of the Belfast Commissioning Group, Maeve Hully, chief executive of the Patient Client Council and the DUP's Jim Wells, vice chair of the assembly health committee.
In a statement on Friday afternoon, the DUP said: "We charge an administration fee to cover the room hire and lunch provided for every event at the conference and this is no different.
"No-one attends conference free of charge and no one leaves disappointed with our programme.
"Conference is not open to members of the public - there is no question of members of the public being asked to pay to see any DUP Minister or MLA.
"Anyone wishing to see our ministers and members are able to do so in the constituency or at the assembly any day of the week."
However, Sinn Fein's Alex Maskey said the charge was "quite disgraceful" and should be withdrawn.
"I think it's fraught absolutely with ethical problems, political problems and maybe even legal problems," he said
"What we're looking for here is democratic, acceptable and accountable government, not some type of pay per view.
Referring to the Republic of Ireland's Fianna Fail party he added: "The only party that I know on this island which was charging people to come and talk to their minister ended up almost destroyed at the last election."
'Overstepped the line'
The UUP's John McCallister said while other parties charged people to attend their conferences, this was different to charging over one specific issue.
"Some might say 'is this the first health charging we're bringing in' when you have to pay to see the minister," he said.
"It's the way they've overstepped the line on this, it just smells of (paying for) access to the minister.
"It blurs the line between government and the party political process."
The SDLP's Delores Kelly said she thought the charge was "appalling".
"There could be perceptions that the minister's stamp on this independent review could be picked up by those paying £50 to attend this seminar," she said.