Landlords and tenants seeking clarity on whether properties are exempt from caps on rent increases in designated Rent Pressure Zones will be able to look to new guidelines from the Residential Tenancies Board.

The guidelines also outline what constitutes "substantial refurbishment" for the purposes of using it as a reason to remove a tenant.

The clarification comes after the housing agency, Threshold, raised concerns earlier this month, about the number of landlords citing substantial refurbishment as grounds to end a tenancy.

The housing charity said it had been contacted by more than 200 tenants about the issue this year.

"Landlords evicting tenants from their homes on the grounds of 'substantial renovation' is an issue that clients have been coming to Threshold with for a number of months now," said John-Mark McCafferty, Threshold chief executive.

Mr McCafferty said that the charity broadly welcomed the guidelines, particularly around 'substantial renovation', however, he reiterated its call for the term to be given a legal definition.

Mr McCafferty said: "We are concerned that these are guidelines only, and the language used is vague, open to interpretation, and offers landlords combinations of works that may or may not constitute a substantial change. This lack of certainty will result in disputes and will not provide much comfort for our clients in these situations."

Rosalind Carroll, director of the Residential Tenancies Board, said: "The key point for people to understand is that for the exemption to apply, there needs to be a substantial change in the nature of the accommodation being provided, so it is not just about improving a property but about significant changes; for example, has the property been extended."

Sinn Féin housing spokesman Eoin Ó Broin has criticised the new guidelines, saying they "are not worth the paper they're printed on".

Mr Ó Broin said: "There is simply no justification for landlords who undertake substantial refurbishment from being exempt from the rent pressure zone cap. They can already write these costs off against their tax liability."

He said he was "also concerned that the onus for policing these new guidelines will rest with the tenant.

"This is not acceptable or fair on tenants, especially more vulnerable tenants."