Former industry minister David Emerson said his decision to defect from the Liberals and take a cabinet post in Prime Minister Stephen Harper's government was made to better serve his constituents.

The Vancouver MP and former head of lumber giant Canfor stunned onlookers when he arrived at Rideau Hall shortly before the Tory cabinet was to be announced Monday.

Soon after, he was sworn in as the new Conservative Minister of International Trade and the Minister responsible for the Olympic Games in Vancouver in 2010.

He defended his position at a brief press conference late in the afternoon.

"I fundamentally went through the thought processes many times over, and came to the conclusion I can be more helpful to the people of my riding, the people of my city, the people of my province and the people of my country doing this, as opposed to being in opposition and trying to become a powerful political partisan which I have never been," Emerson said.

Emerson said he originally entered politics at the behest of former prime minister Paul Martin. At that time he was not a Liberal, but decided to enter politics to serve the people of his riding.

He said he would have "absolutely" stayed on in Paul Martin's cabinet if the former PM had been re-elected.

One reporter demanded to know how Emerson could go from knocking on doors and banging in signs for the Liberal Party, to representing the opposition, within only a few weeks.

"I was elected to serve the people of Vancouver Kingsway," Emerson answered. "I will continue to serve them as the member of Parliament for Vancouver Kingsway.

"I have always served the people of my riding on a non-partisan basis, I run my office there on a non-partisan basis because I was running as a Liberal and I ran because I was encouraged by prime minister Martin."

On election night, however, Emerson told his supporters things like "We have got to look at this as Ground Zero for rebuilding a stronger, more vibrant, healthier, winning Liberal Party," and added to journalists, "I would like to be Stephen Harper's worst nightmare."

Retribution?

Snatching Emerson could be seen as Conservative retribution for the defection of Belinda Stronach to the Liberals in exchange for a cabinet post.

At the time, Harper harshly criticized Stronach and several Conservatives demanded laws forcing floor-crossers to go back to the electorate for another mandate. However, there is nothing in the Conservative platform about regulating how MPs could go about switching parties.

Opposition Leader Bill Graham told CTV Newsnet that Stronach left the Conservative Party for policy reasons, and Emerson's defection isn't comparable.

He did say the move seems to clash with Harper's earlier position.

"I think for him to have gone out and sought out David Emerson in the way which he did is really flying in the face of a lot of positions he had taken," Graham said. "I know some of his own backbenchers are upset about this, because this is the kind of deal-making that they spent time criticizing."

Harper said he approached Emerson based on merit.

"During the last parliament, as I sat across from the government benches, I was consistently impressed with David Emerson," Harper told reporters after being sworn in as Canada's 22nd prime minister.

"He is a man of great intelligence, a man with a stellar record in the private sector, who is clearly committed to public service.

"I asked Emerson to join Canada's new government and he accepted. For this I am grateful and I know Minister Emerson looks forward to continuing to serve the people of British Columbia and all new Canadians in the next Parliament."

New Democrat leader Jack Layton said Harper's controversial decision to appoint a cabinet minister who was elected as a Liberal flies in the face of his election pledge to clean up government.

Layton said MPs who cross the floor to another party should be forced to return to their constituents for a by-election in order to remain in office.

Anne McLellan, the former Liberal deputy prime minister who lost her seat in the election, said Emerson's defection shocked her and others in the party.

"Certainly, based on what I'm hearing, no one, or very few people had any prior knowledge that he was going to do this," McLellan told CTV Newsnet.

McLellan added, however, that Emerson was not looking forward to the prospect of being an opposition MP.

"I talked to David after the election and I know there was no question he was not looking forward to sitting as an opposition member. He told me that he'd come to government, or that he'd come to Ottawa to be in government and try and do some positive things," McLellan said.

Some Liberals saw Emerson as a potential leadership candidate. In the recent campaign, Emerson was featured in televised Liberal election ads promoting the party in British Columbia as the right choice for voters.

His acquisition by the Conservatives gives the party its only elected MP in the major urban centres of Toronto, Montreal, and Vancouver.

"It is a big score for us, no doubt about it," said Conservative strategist Tim Powers.

Upset constituents

The Vancouver Kingsway riding where Emerson was elected has been a Liberal stronghold for more than a decade. In fact, the third-place Conservative candidate in the January election only received 18 per cent of the vote.

Many of Emerson's constituents were dismayed at Emerson's sudden change in loyalties. Several told CTV Vancouver had they known he was going to switch to the Tories, they wouldn't have voted for him.

John McNamee, Liberal riding secretary in Vancouver Kingsway, told CTV's Canada AM on Tuesday that Emerson needs to seek a new mandate from voters.

"The Conservative candidate (in Vancouver Kingsway) was a distant third, and I don't think if David Emerson had run as a Conservative  he would be here today."

With a report from CTV Vancouver's Rob Brown