A council meeting was abandoned when a protester from Extinction Rebellion abseiled from the public gallery.
The Cambridge City Council budget meeting was brought to a halt on police advice, according to the Local Democracy Reporting Service.
Council leader Lewis Herbert said the act "delayed the council agreeing plans to tackle the climate emergency".
Protestors said they wanted the council to cut ties with fossil fuel and set up "peoples' assemblies".
Labour leader Mr Herbert said: "Their actions delayed the council agreeing 2020 plans to tackle the climate emergency and cut carbon emissions, including peoples' assemblies to involve residents and businesses to act now to cut their emissions.
"If Extinction Rebellion really want to mobilise Cambridge, they need to think what will best motivate local residents to act and win their support, and consider that in deciding their actions over the next week."
Tilly Porter, who took part in the protest, said: "We will stand our ground... until they agree to do enough to address the climate emergency."
The meeting was abandoned but protesters changed into their pyjamas and spent the night in the chamber before leaving in the morning.
Here’s a pic of one protester getting ready for bed in the Cambridge City Council chamber last night. I’m hearing they left around 6:30am. Don’t know if they ever managed to turn the lights off pic.twitter.com/Ck2C6dKOi3— Ben Hatton (@BenHattonJourno) February 14, 2020
Cambridgeshire Police said the protest was "peaceful" and no arrests were made.