NEW YORK CITY - President Donald Trump's foundation served as a personal piggy bank for his businesses, legal bills and presidential campaign, New York's attorney general said Wednesday as she sued the charity, Trump and three of his children.

The Donald J. Trump Foundation "was little more than a checkbook for payments from Mr. Trump or his businesses to nonprofits, regardless of their purpose or legality," Democratic attorney general Barbara Underwood said as she sued to dissolve the foundation and seek $2.8 million in restitution.

The lawsuit says the foundation illegally helped support the Republican's campaign by raising money at a nationally televised fundraiser in January 2016, then allowing campaign staffers to dictate how the money was spent in grants.

Foundation attorney Sheri Dillon and a Trump Organization spokeswoman didn't immediately respond to messages seeking comment. She still represents the foundation. Mr. Trump defended himself on Twitter, calling the suit "ridiculous." 

Underwood's predecessor, Democrat Eric Schneiderman, began investigating the foundation in 2016 following Washington Post reports that foundation spending personally benefited the presidential candidate. Schneiderman ordered the foundation to stop fundraising in New York.

The Trump campaign, at the time, said the foundation intended to cooperate with the investigation. The campaign had previously called Schneiderman "a partisan hack" who backed Trump's 2016 Democratic rival, Hillary Clinton. Schneiderman resigned from office last month after The New Yorker reported that multiple women had accused him of sexual assault and harassment.

© 2018 CBS Interactive Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.