VANCOUVER -- The latest court battle waged against the British Columbia government by the teachers' union could ding taxpayers for $6 billion to start, the province says.

That cost will be ongoing because the union's demands to have its contract provisions restored to 2002 levels regarding class-size limits and staffing ratios would require more funding, the government said in court documents as part of a B.C. Supreme Court trial starting Monday.

The Liberals stripped the teachers' collective agreement in 2002 when it bypassed the collective bargaining process and enacted legislation that led the union to launch two successful court challenges.

In the second ruling in 2011, a B.C. Supreme Court judge said the government did not have the authority to gut bargaining rights guaranteed in the charter.

Even the B.C. Teachers' Federation agrees in court documents that reinstating the provisions will cost much more than the government's initial $500 million estimate.

"It is theoretically conceivable that the damages could be most closely approximated by the very lengthy proceeding," the union said. "It would require that in the case of the class size provisions, this court determine which of the tens of thousands of classes in the various school districts exceeded the class size numbers."

In her 2011 ruling, Justice Susan Griffin gave the province a year to come up with a remedy. But after 13 meetings with the teachers' union failed to lead to an agreement, the government introduced new legislation that included $200 million in funding, which was rejected by teachers.

They complained the money benefits support staff unions, the government's court documents said.

"The BCTF complains that (the fund) was 'extensively utilized to the benefit of members of the support staff unions and points out that the support staff union (CUPE) managed to negotiate a prescribed allocation of (the fund) to its members as part of its collective agreement."

The government said in the documents that its objective was to provide additional classroom support to teachers and students, whether in the form of additional teachers or education assistants.

The union "declined to ever engage with government meaningfully" on how the funding could be maximized to benefit complex classrooms, the documents said.

But the union said "the purported repeal of the unconstitutional legislation was in any event not a true repeal but a sham. Instead of responding to the decision, the province had the audacity to merely continue the provisions, which this court found to be unconstitutional and invalid."

"The teachers will ask the court to find that unconstitutionally deleted provisions of the collective agreement are reinstated, the right to collective bargaining is retroactively reinstated, and to provide damages sufficient to remedy the harm caused by the government's breach of teachers' fundamental freedom of association."

While the teachers' union has accused the government of acting in bad faith, the government has responded that the union had no interest in coming to an agreement regarding its legislation deemed unconstitutional.

"The parties' failure to reach a settlement agreement was due to the conduct of the BCTF, which was not consistent with good faith consultation," the government said.

The 2002 contract-gutting legislation also included health-care workers, who along with teachers, launched a Supreme Court of Canada challenge against the province and won their case five years later.

In 2008, the government shelled out $85 million in compensation to four health-care unions, including the Hospital Employees Union, which received $68 million of that money.

However, there was no agreement between teachers and the province.

Teachers have been without a contract since June, and negotiations are currently on hold pending the court case, which is scheduled for 19 days.

Premier Christy Clark, who was education minister in 2002, has proposed a 10-year-deal, saying that would ensure children's education would not be disrupted by labour disputes.

But the union has dismissed that path as ludicrous, saying it's another attempt by the government to further strip teachers of their working rights.

Meanwhile, 27,000 school support staff, including education assistants, bus drivers and trades workers, are also seeking a new contract and have asked for a wage hike.

Education Minister Peter Fassbender has said any pay increases would have to come from savings in existing budgets in keeping with the government's current policy for all public-sector employees.

A year-long teachers' strike two years ago saw them refusing to fill out report cards or do administrative duties such as supervising children in playgrounds.

The teachers' one-year contract expired at the end of June.