Property agents Savills says extra financial documents were requested from potential home buyers, to help deal with the high demand for viewings.
The Data Commissioner is in touch with Savills after it emerged they asked people to disclose the full amount of their mortgage approval before viewing a house.
Potential buyers of a new property development in Dublin were asked to provide evidence of the full amount of mortgage approval as well as savings or gifts from family.
Savills faced backlash from commentators who said the property agents were seeking too much information just to view a property.
But today, the firm says that over 5,000 people were looking to view 44 houses at the Somerton development in Lucan and the extra information was needed to make the process more efficient.
An auctioneering representative body says a universal mortgage approval system is needed to create a more efficient property market in Ireland.
Chief Executive of the Institute of Professional Auctioneers and Valuers Pat Davitt said all banks should come together to come up with an agreeable loan approval system.
"It wouldn't maybe specify the amount of money but would specify that people could buy a property that they are looking at," said Mr Davitt.
Paul Merriman from AskPaul.ie said property buyers "shouldn’t be surprised" when agencies ask for detailed financial documents prior to a house viewing.
He said the real issue is the country's inadequate housing supply.
"I think the fact that 5,000 people are going for 44 houses is an outrage," said Mr Merriman.
People should be putting pressure on the Government to get planning permission through quicker, to build quicker and to promote building, he said.