Union president John Strohmaier says paramedics will no longer work any hours outside of their regularly scheduled shifts. (CBC)B.C.'s striking ambulance paramedics are stepping up job action, saying they will no longer work any extra hours outside of their regular shifts.

The province's 3,500 paramedics have been on strike since April 1, but are not allowed to withdraw their services because of essential service legislation.

They're asking for better staffing levels and wage parity with other emergency responders.

More than 400 ambulance paramedics and union supporters staged a massive rally Friday at the Richmond Oval, one of the Lower Mainland's main Olympic venues.

It comes after the government rejected a settlement offered by paramedics earlier this week, saying it was too rich.

Speaking at the rally, union president John Strohmaier was careful not to call the move a ban on overtime.

But he did say that as of 6 p.m. PT Friday, paramedics would only work their regularly scheduled hours.

"This is a direction from the union that our members only work for the shifts they signed up for … That's the employment contract we signed up for and we are going to live up to that contract," he said.

Paramedics burning out, union says

The union says there are hundreds of vacant paramedic positions across the province, and the system relies heavily on overtime to fill that gap.

Hundreds of striking paramedics and union supporters staged a protest at the Richmond Oval Friday. (CBC)Strohmaier said his members are burning out from working excessive hours, and urged the government to act on its claim that hundreds of people are waiting to fill those jobs.

Meanwhile, the CEO of Vancouver's 2010 Olympic organizing committee said if the paramedic strike continues during the Games, an alternative plan would be put in place.

But John Furlong said he is confident emergency responders and the government will come to an agreement prior to the Olympics.

"Listen, I think everyone is aware of what's happening, that the Olympic games are coming, and this matter needs to be settled by the people responsible for it," he said.

"We're going to do our best to continue to plan and if we get to a situation where we have to improvise, we'll do that, but hopefully we won't have to."