New York's Attorney-General is suing the Donald J. Trump Foundation, US President Donald Trump, and others, and is seeking to dissolve the foundation after what she called its "persistent illegal conduct" over more than a decade.

Attorney-General Barbara Underwood says the foundation engaged in "extensive unlawful political co-ordination" with Trump's 2016 presidential campaign, conducted "repeated and wilful self-dealing" to benefit his personal and business interests, and violated "basic legal obligations" for non-profits.

The lawsuit was filed with the New York State Supreme Court in Manhattan on Thursday.

Others named in the action are Trump's sons Donald Jr and Eric, and his daughter Ivanka.

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"As our investigation reveals, the Trump Foundation was little more than a chequebook for payments from Trump or his businesses to non-profits, regardless of their purpose or legality," Underwood said in a statement.

"This is not how private foundations should function and my office intends to hold the Foundation and its directors accountable for its misuse of charitable assets."

The suit seeks restitution of US$2.8 million ($4m) and the shutdown of the foundation, as well as a 10-year ban on Trump serving on the board of any other New York charity.

Trump has slammed the lawsuit as "ridiculous" and says he won't settle.