B.C. Premier Gordon Campbell announced Wednesday that he will step down from office, and is calling for a leadership convention as soon as possible.

The move comes as Campbell's polling numbers have plummeted over the much-maligned harmonized sales tax, which has led to intense speculation about his political future.

"Over the last few weeks, our government has continued to move forward with initiatives that will create jobs, strengthen our economy and support families in every region of British Columbia," Campbell told reporters, making note of last week's announcement of a 15 per cent personal income tax cut.

"It is clear to me that those initiatives have been overshadowed. And when public debate becomes focused on one person, as opposed to what's in the best interest of the province of British Columbia, we've lost sight of what is important. When that happens, it's time for a change."

Campbell declared his intentions mere hours after calling a press conference for 11:30 a.m. local time to make an "important announcement."

Campbell has come under fire from voters, opposition politicians and even members of his own caucus over the unpopular HST, which came into effect on July 1.

The move sent Campbell's popularity plummeting: only 12 per cent of respondents to an Angus Reid poll conducted in September said they approved of his job performance. More recent polls put Campbell's support into single digits, a mere 9 per cent, for the first time in his three terms in office.

Prime Minister Stephen Harper thanked Campbell for his public service in a statement today, listing the premier's accomplishments, including his support during the global economic downturn and his leadership during the Winter Olympics.

The statement made no mention of the HST.

Conservative MP Stockwell Day, the president of the Treasury Board and the minister responsible for B.C., called Campbell a "great Canadian" in remarks to reporters in Ottawa.

"He was unfailing in putting first and foremost, the interest of British Columbians, the interest of the province," he said. "It's been an honour and a joy to work with him on so many items."

In early September, Campbell said he would not step down despite calls for his resignation from former energy minister Blair Lekstrom and Liberal supporter Scott Nelson.

Lekstrom resigned from cabinet last spring, saying he had to listen to the concerns of his constituents who felt the government badly mismanaged the HST issue.

Campbell was further hammered over the income tax cut, which critics called a move designed solely to pander to angry voters.

The premier did, however, concede to sending the HST to a referendum after former premier Bill Vander Zalm collected more than 700,000 signatures on a petition to send the issue to voters. The referendum is scheduled for September 2011.

During his brief remarks on Wednesday, Campbell urged voters to reconsider the tax, which he has long defended as good for the province.

"I am hopeful that my announcement today will allow British Columbians to move forward and fully consider the HST and its alternative as they move toward September of 2011," Campbell said.

"It's not always popular to do what you think in your heart is right, and in the long-term interests of our province and the families who live here."

Political commentator Michael Geoghegan said Campbell was a "capable leader" whose economic policies allowed B.C. to weather the global economic meltdown.

But it was an economic policy move, the implementation of the HST, that was his undoing, primarily because it was implemented without public consultation.

"It was a situation where, from a policy standpoint an argument could certainly be made that it would make British Columbia more competitive," Geoghegan told CTV News Channel. "The key mistake was not having that discussion prior to implementation."

Campbell, who led three consecutive majority governments, was also facing a leadership review at the B.C. Liberal Party convention later this month and a revolt within his own caucus.

CTV's Rob Brown said a rumour began last weekend "of an urgent and unusual" caucus meeting that was to be held this week. While that rumour was shot down, there "undoubtedly have been some backroom dealings and negotiations about departure date and pressure from the party, probably the executive and members within the Liberal caucus," Brown reported.

Political watchers found evidence of a possible caucus revolt in last week's cabinet shuffle. Embattled Finance Minister Colin Hansen, who was in the post when the HST was introduced, was allowed to keep his job, as was Energy Minister Bill Bennett despite his public complaints that his department had been stripped of some powers without consultation. The Bennett decision in particular made Campbell, known for being a top-down leader with strict control on his cabinet, appear weak to some observers.

Campbell, who did not address the media on Wednesday beyond his prepared remarks, is expected to take questions from reporters Thursday morning.

Despite his plummeting popularity, Campbell thanked British Columbians for allowing him to serve for so long, and his entire family, in particular his wife Nancy and their children, who he said "have all paid a price for my 26 years of public service.

"Politics can be a very nasty business, and at times, that nastiness spilled over into their own personal lives. For that, I am sorry," Campbell said.

"I have always felt that public life is incredibly important. It's what defines us as British Columbians, it's what defines us as Canadians. I feel blessed to have had the opportunity to serve in this position longer than most of my predecessors and to have been part of this incredible time in British Columbia's history. It's been quite a run, and a lot more fun than not."