Extinction Rebellion have asked for donations from the public for their London protesters, including "ready-to-eat vegan food" and camping equipment.
In an appeal on Twitter, the campaign group wrote: "Extinction Rebellion are holding sites across Westminster. Their overnight rebels need hot water, ready-to-eat vegan food, tents, sleeping gear and warm clothes.
“Please help them. Many are preparing to go on hunger strike so they need some food now.”
However, their appeal has been met with criticism, with some saying the activists should have been more prepared for their two-week-long protest.
Others have said their plea for help is insensitive to homeless people; just last year, 43-year-old homeless man, Gyula Remes, died opposite the Houses of Parliament.
One Twitter user wrote: “Approx 9,000 people are forced to sleep rough in London due to homelessness – Extinction Rebellion asking for ‘ready-to-eat vegan food’ categorically *not* a good look.”
Another said: “You really are not helping the cause (which I support on the whole). If you were planning to be out all night you should have been prepared.
“There are enough homeless out at night who genuinely need food and shelter and blocking access to a hospital was unforgivable.”
Extinction Rebellion campaigners are calling for urgent government action against climate change - and at least 300 people have been arrested since the protests kicked off on Monday.
Around 30,000 Extinction Rebellion demonstrators from around the country are expected to congregate in the capital to take part in the 14-day protest.
The action is the group's second international demonstration - the first was in April, and saw more than 1,000 people arrested in London.