The new senators are Diane Bellemare of Quebec; Tobias C. Enverga Jr. and Thanh Hai Ngo, both from Ontario; Thomas Johnson McInnis of Nova Scotia; and Paul E. McIntyre of New Brunswick.
"Their broad range of experience and dedication to community will further strengthen the institution and benefit the entire country," Harper said in a news release.
The NDP reacted with scorn.
"Stephen Harper once said: 'An appointed Senate is a relic of the 19th century.' Well, we now know what century he’s living in," said Charlie Angus, the party's ethics critic.
"And Harper has got himself on the Top 10 list of most unaccountable senator appointments by a single prime minister. It’s a shameful record of hypocrisy."
Harper has so far appointed 51 senators, Angus said.
Bellemare is an economist and author who ran unsuccessfully three times as a candidate for Action Democratique du Quebec.
Enverga is a project manager at the Bank of Montreal and a major player in the Filipino-Canadian community.
Ngo is a Vietnam-born teacher who has also been a citizenship judge and is involved with a number of Vietnamese-Canadian organizations.
McInnis is a Halifax lawyer and businessman who sat in the provincial legislature as a Conservative for 15 years. He ran unsuccessfully for the federal Tories in the 2000 election.
McIntyre is a lawyer and community activist who writes poetry in his spare time.
The prime minister says the new senators are pledged to support his government's efforts to reform the Senate, including term limits.
The appointments give Harper's Conservatives 62 of the Senate's 105 seats. The Liberals hold 40 seats, while there is one Progressive Conservative senator and two independents.
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