B.C. Premier Christy Clark says the only thing the defection of John van Dongen from the Liberals will accomplish is to make it easier for the oppostion NDP to get elected.

Van Dongen, a former cabinet minster, quit Monday to join the B.C. Conservatives after accusing Clark of a failure of leadership.

But Clark says leadership is about making sure B.C. residents have a free-enterprise coalition to vote for, and her job is to ensure that coalition stays together.

She says van Dongen has made a bad decision that will favour the NDP and she doesn't believe his defection will lead to other B.C. Liberals following suit.

But the B.C. Conservatives have also been celebrating van Dongen's decision to become the first Conservative MLA in the legislature since since the mid 1980s.

Van Dongen has been the MLA for Abbotsford South for 17 years, but his speech in the legislature contained thinly veiled criticism of the job Clark has done as premier.

At a news conference afterwards with B.C. Conservative Leader John Cummins at his side, van Dongen attacked Clark directly about the BC Rail deal and said he has hired a lawyer at his own expense to investigate her.

Liberal House Leader Rich Coleman was highly critical of both what van Dongen did Monday and how he did it.

"I thought what he did yesterday in the house was an abuse of the legislature to start with," Coleman said Tuesday.

Coleman knew van Dongen was planning to leave, but not that he would attack the premier's character.

"He went into a diatribe that was unexpected and basically questioned my integrity and every other member's integrity and honesty," said Coleman.

Weakening in polls

An Angus Reid public opinion poll released Tuesday had more bad news for Clark.

Her approval rating has fallen by nine points since August and now sits at 33 per cent, the poll suggests.

The poll was part of a national survey taken between March 6 and March 14 among 6,622 Canadians. The margin of error is considered plus or minus 1.2 per cent 19 times out of 20.

The question was, "Do you approve or disapprove of the performance of British Columbia Premier and B.C. Liberals leader Christy Clark?"

With files from the CBC's Stephen Smart and Jeff Davies