Western Australia’s government says it will not be backing down on controversial shark-cull plans, despite a large anti-cull protest at the weekend.

More than 4,000 people gathered at Perth’s Cottesloe Beach on Saturday to vent their anger about the plan to use baited lines to kill large sharks off selected swimming beaches.

The cull plan – which the government says will only target sharks over three metres – was announced after seven fatal shark attacks off the WA coast in three years.

WA’s acting premier Kim Hanes says the Government is not budging.

“We believe the Government is doing the right thing,” he said.

“We’ve had seven people that have lost their lives in our water in the last three years compared to [only 20] over the last 20 years.

“So the numbers have significantly increased in the last three years and we believe the Government had to do something about it.”

Environmentalists argue there is overwhelming evidence that killing sharks will not prevent attacks.

“There is going to be other marine life caught in the bait lines, not just sharks and there’s going to be sharks under three metres also caught in the bait lines,” protest organiser Natalie Banks said on Saturday.

“We are ruining the marine ecosystem.”

The deadline for contractors to tender for the culling contract expired at the weekend.