Housing agency Threshold has said it is concerned by the number of landlords seeking to move tenants out so they can carry out renovations.
The agency said 2,000 people have contacted it about termination notices issued by landlords so far this year.
It said more than one in ten related to landlords seeking to carry out substantial renovations and wanting the tenants to leave.
The agency said it was concerned some landlords were using a loophole in the law that allows them to terminate a tenancy and re-let the property at a higher price without carrying out any major renovations.
In a statement, the Residential Tenancies Board said it would shortly publish guidelines for landlords and tenants on what constitutes substantial refurbishment.
One in five of the queries to Threshold related to termination requests because a landlord wanted to move a family member into the property and nearly half were due to a property being sold.
