A Melbourne woman and her friends have made 1,000 badges bearing the #illridewithyou hashtag to hand out to commuters in the city.

The hashtag, which began trending worldwide on Twitter on Monday, was created to counter a potential anti-Muslim backlash over the Sydney siege.

Users tweeted messages declaring they would ride with anyone who was scared to take public transport because they were wearing religious dress.

Stephanie Speirs said she initially posted the idea as a comment on an article she saw on Facebook about the social media movement.

Ms Speirs said she thought a badge would be a good real-world way to let commuters know they were supported, and that racial comments would not be tolerated.

"A lot of people said that's a great idea," she told 774 ABC Melbourne's Dave O'Neil.

"I sort of felt like I couldn't really come up with a good reason not to do it."

After sending emails to a number of badge companies, one wrote back offering to donate the hire of a badge-making machine and enough supplies to make 1,000 badges.

Ms Speirs said it took her and her friends six hours to make all 1,000 badges, which they planned to hand out to commuters at Melbourne's Flinders Street Station.

'Why not make a real-world hashtag?'

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Ms Speirs said it was important to her that the #illridewithyou movement had a life outside of social media.

"I realised that it was all happening online," she said.

"There's a lot of people that might not be using Facebook or Twitter that maybe need that offer of assistance.

"Why not make a real-world hashtag as well?"

She hoped the badge would encourage others to speak up if they saw someone being harassed on public transport.

"Often people all hold their breath and look at each other and go 'who's going to say something?', and sometimes no-one says something," she said.

"This is a good way for us to know, 'hey, if I intervene, there's some other people there that might back me up'."

She said the badge also sent a message to anyone who thinks racist or abusive behaviour is acceptable.

"Its saying to them 'I don't agree with you'."