Illinois ex-congressman Jesse Jackson Jr, son of the civil rights leader, pleaded guilty Wednesday to charges related to illegally spending hundreds of thousands of dollars from his campaign coffers.

He entered a guilty plea at a federal district court in Washington on charges of conspiracy to commit false statements, mail fraud and wire fraud, the Washington Post reported.

Court documents released earlier Wednesday detailed how Jackson and his wife were involved in using 750,000 dollars from his campaign fund for personal expenses, including the purchase of a 43,000-dollar watch and other luxury goods. His wife, Sandra Stevens Jackson, was expected to plead guilty to a related charge of filing false tax returns.

The younger Jackson has spiralled through a series of health and legal problems and resigned in November from his seat in the US House of Representatives, just days after winning reelection.

Jackson's father, who waged ground-breaking campaigns for the Democratic Party's presidential nominations in 1984 and 1988, said Monday that his son was "under tight medical supervision" for bipolar illness.

Jesse Jackson Jr has said he suffered bipolar depression, for which he has been under treatment and was already on leave from Congress starting in June 2012 until his resignation.

Jackson was under investigation by the House Ethics Committee for his alleged attempt to bribe his way into an appointment to the US Senate seat that was vacated by US President Barack Obama after his election to the presidency in 2008. Obama had two more years in his term.