In New York City, landlords looking to renovate are supposed to tell the Buildings Department whether their tenants are protected by rent regulations. The idea is to prevent harassment by owners seeking to force renters out in order to charge more. But the Buildings Department does not always check to see if the landlords are telling the truth.

Aaron Carr, however, does.

Mr. Carr, 30, is the founder of a start-up tenant watchdog agency, the Housing Rights Initiative, and his specialty is searching public records at state and city agencies to expose what he says is a broken system of tenant protections.

On Monday, Mr. Carr’s latest report is scheduled to be released at a news conference on the steps of City Hall with City Councilman Ritchie Torres of the Bronx. According to H.R.I.’s research, on more than 10,000 building permits filed with the city over the past two years, landlords lied about whether there were rent-regulated tenants in their buildings — and got away with it.

Mr. Torres said that the city, which has made affordable housing a priority, should shoulder an equal amount of the blame. “Just as scandalous as the number of falsified permits is the failure of enforcement by the Department of Buildings,” he said.