MORE than a third of MLAs who rent out residential properties were not registered as landlords when checked by the Irish News.
Five out of the 16 assembly members who declare rental properties did not appear as registered under the compulsory landlord registration scheme.
The scheme allows tenants, neighbours and councils to identify landlords in a bid to increase accountability.
All private landlords must register or face a fixed penalty of up to £500, or a fine of up to £2,500 if brought to court.
Nicola McCrudden, director of the Chartered Institute of Housing for Northern Ireland, said MLAs "should be leading by example".
"It is very concerning if any of our legislators are not meeting even the basic legal requirements," she said.
"The assembly approved registration in principle in 2011 but registration has been mandatory since February 2015 so there has been plenty of time to act.
"It's hard to see a legitimate reason for an MLA who is a landlord to not be aware of their obligations."
Two Sinn Féin MLAs, two DUP representatives and an SDLP assembly member declared residential rental properties but their names did not appear on the register.
DUP regional development minister Michelle McIlveen has declared residential properties in Belfast and Newtownards.
Former DUP health minister Jim Wells has a half-share in two residential properties in Co Down.
In Sinn Féin, West Belfast MLA Pat Sheehan declared four Belfast properties while constituency colleague Rosaleen McCorley has a half-share in a house in the city.
And the SDLP's Upper Bann representative Dolores Kelly disclosed a residential property in Belfast.
Last night Ms Kelly insisted both she and her husband have registered, paid their fees and received a landlord registration certificate.
The DUP last night said Ms McIlveen's name has since been added to the register.
"There was a problem with the activation of Michelle McIlveen's landlord account. An account was created in September 2014 and she received all regular information updates. This has now been rectified," a spokesman said.
He added: "Mr Wells's wife suffered a serious stroke around the time landlord registration became mandatory and as a result the registration process was not completed for some family-owned properties. Steps are being taken currently to resolve this."
A Sinn Féin spokesman said Mr Sheehan's properties are registered under a management company.
The spokesman added that Ms McCorley has a 'half-share' with MLA Sean Lynch, who is registered as a landlord.
He said both had initially registered but were advised by registry officials to only put one name forward.
The Department for Social Development said: "Where someone's properties are overseen by a management company or agent, that person is required to be registered as a landlord and their name appear on the landlord register."
A spokeswoman added that joint owners are required to register and provide details of each owner.
Sinn Féin added that a rental property declared by North Antrim MLA Daithí McKay was sold two years ago and his register of interests will be updated.