The Andrews government has given public servants the green light to down tools and join a climate rally expected to bring much of Melbourne's CBD to a standstill on Friday.

The Department of Premier and Cabinet sent out an email saying a number of public servants wanted to attend the 2pm march and could ask for "flexible working arrangements".

School students striking for climate change also received the backing of the Premier's department, which said their actions should be celebrated.

Scenes from the climate rally in Melbourne in March. Credit:David Crosling

Protesters calling for greater global action will gather at Treasury Gardens at 2pm and march from 3pm to Collins Street towards Exhibition Street and then on to Flinders Street and back to their starting point.