Action taken over WA gas site 'bullying'

The major contractor at Chevron's massive Wheatstone gas project in WA's north says it has taken action after more than 250 workers signed a petition alleging serious workplace bullying.

The Australian Manufacturing Workers Union says a worksite manager for US engineering giant Bechtel used profanity and bullying tactics when speaking to employees last month, including referring to workers as "rats" and "no better than paedophiles".

"Bechtel takes all matters of this nature very seriously. On this particular occasion, a thorough investigation was conducted and appropriate action has been taken," the company said in an emailed statement.