Six police cars, six fire trucks and a hazmat unit have been called to the office of Liberal MP Craig Laundy after he received an envelope full of glitter from same-sex marriage campaigners.

The emergency response was triggered after staff at the Member for Reid's Sydney office mistook the package for a suspicious substance.

In what it is calling a "glitter protest", activist organisation GetUp! has been sending the envelopes to government MPs after a Coalition party room meeting blocked a free vote on same-sex marriage.