Mayor Bill de Blasio is defending the privately-funded non-profit organizations tied to his administration after a government watchdog group demanded an investigation. Common Cause New York says the mayor is making a mockery of the city's campaign finance laws and may be running afoul of the City Charter. The group is also raising questions about the mayor's reliance on outside advisors. That's an issue we examined at NY1 in an investigative report last year.

Mayor de Blasio and his top aides may officially run City Hall, but a leading government watchdog group says it is growing increasingly concerned that a well-financed shadow government is springing up and exerting significant influence over public policy.

"Here in New York we expect our elected officials to work first and foremost for the people," said Susan Lerner Executive Director of Common Cause New York. "This shadow government is not anything which should be permitted."

In a five-page letter to the city's Conflicts of Interest Board and the city's Campaign Finance Board, Lerner's group is calling for an investigation into the non-profit organizations linked to the mayor. They have been raising unlimited sums of money from real estate developers and unions, among others.

The American Federation of Teachers, for example, gave the mayor's Campaign for One New York group $350,000. The city's campaign finance laws prohibits contributions greater than $4,950.

"I think for most New Yorkers they don't expect city business to be done through a shadow government and they certainly don't expect that dark money is a necessary part of a modern mayoralty," Lerner said.

The mayor says non-profit groups like the ones supporting his agenda have been around for a long time.

"The idea that organizations would come together to fight for full-day pre-k for all and affordable housing I think is understandable and makes a lot of sense," de Blasio said.

And he argues against the idea that there is "dark money" at play here. The organizations linked to the mayor have voluntarily disclosed their donors.

Common Cause is also raising questions about the mayor's reliance on outside advisors who also represent paid clients who have business before City Hall. The mayor says he does not allow his ongoing outside advisors to lobby him.