Thousands came together at City Hall on Monday, calling on Mayor Bill de Blasio to build more affordable housing and punish slumlords.

More than 5,000 people demonstrated, many of whom said the mayor needs to fulfill a campaign promise from four years ago to increase access to safe affordable housing.

Some said they are forced to pay about 30 percent of their income to live in substandard conditions.

"We're here today from a community of people in churches fighting for our rights and what he promised us. You can't promise and not follow through," said one demonstrator.

"A lot of people are homeless and cannot afford housing. The rents are sky high. And that's a reason why we have to stand strong because we just can't afford it, you know? I've been there and that's why I'm here for others today," said another participant.

The rally drew elected officials and many low-income New Yorkers. Metro IAF — a not-for-profit coalition of religious groups and advocates for seniors and housing — organized the rally and backs a plan to build 15,000 affordable housing units for seniors on dozens of properties already owned by the city.

A spokeswoman for City Hall told NY1 that the mayor supports this mission of expanding access to affordable housing. She said the mayor and agency commissioners have met with Metro IAF and expressed an interest in collaborating.