Hampton retired from the legislature at the 2011 Ontario provincial election[1] and subsequently joined Fasken Martineau DuMoulin LLP as a member of the law firm's corporate social responsibility and aboriginal affairs groups.

Journalist Thomas Walkom has argued that Rae deliberately undermined Hampton's control over the Attorney General's office, staffing the ministry with bureaucrats to which he was ideologically incompatible.

However, Walkom has also noted that Hampton supported Rae's decision to impose a Social Contract of wage restraints and cost-saving measures on Ontario public servants.

This decision was unpopular with some other members of his caucus, including Deputy Leader Marilyn Churley who was a leading supporter of Jack Layton.

After intense lobbying to lower the minimum number of seats for party status, a compromise was reached which allowed additional funding for the NDP and more inquiry opportunities during Question Period.

Ultimately, this controversy was all for nought as on May 13, 2004, the NDP regained official party status in a by-election in Hamilton East, where city councillor Andrea Horwath was elected to fill the vacancy left by the death of Liberal member Dominic Agostino.

The Ontario NDP increased its seat count to nine in September 2006, when well-known local United Church minister Cheri DiNovo won a byelection.

Hampton launched the Ontario NDP's 2007 provincial election campaign at the party's Fresh Ideas New Energy January 2007 policy convention.

[15] Hampton's NDP increased its seat count to 10 in February 2007, when businessman and community activist Paul Ferreira defeated star Liberal candidate Laura Albanese in a byelection in the Toronto riding of York South-Weston.

The NDP's campaign for the $10 minimum wage and its opposition to a controversial 25 per cent pay raise for MPPs were cited as key factors in the upset win.

While there was speculation following the election that he may retire, Hampton announced at the November 24, 2007, NDP provincial council that he was staying as party leader.

[20] In November 2014, Hampton was appointed as a consultant to federal NDP leader Thomas Mulcair on the Northern Ontario Ring of Fire mining development.