A rooftop protest at St Helens town hall will cost the taxpayer £11,000 in repairs alone, council chiefs estimate.
The final total is expected to be much higher once policing and other emergency services costs are factored in.
Tiles were torn from the roof and thrown to the ground during the 10-hour protest.
The damage, described as “considerable”, was caused when a man climbed onto the roof in the early hours of Saturday morning with the aim of staging a protest.
According to witnesses the man, who refused to come down for several hours, was said to be throwing roof tiles and hurling abuse at police while brandishing a banner which read ‘beware the police state’.
The protest threatened to ruin a wedding due to take place at the town hall on Saturday but the man was eventually persuaded to come down and the ceremony went ahead.
A council spokesman said: “Repair work is currently taking place to the town hall roof following an incident on Saturday morning.
“Early on Saturday a man climbed on to the town hall roof with the aim of staging a protest.
“Victoria Square and surrounding streets were closed to the public and a police cordon established. Fire and ambulance crews were also in attendance.
“Central Library was closed and initially it looked as though a wedding scheduled to take place in the town hall on Saturday afternoon would have to be cancelled.
“However, this was able to go ahead as planned when the incident was concluded at approximately 12 noon when the man was persuaded to come down and was then taken into police custody.
“The incident resulted in considerable damage to the roof, with many slates removed and broken.
“The damage is estimated to cost around £11,000 to repair – which the council can ill afford at a time when we are looking for savings totalling £23m over the next two years.”
The man eventually came down at around 11am after the couple made an emotional plea to the protester.
He reportedly came down shouting “should we let them get married?” and the wedding was able to go ahead following an assessment of the damage to the building.
Shaun David Adamson, 33, of Sinclair Avenue, Warrington, appeared at St Helens Magistrates Court on Monday charged with criminal damage of a property and affray.
He was remanded in custody to appear at Liverpool Crown Court on October 5.
It remains unclear what he was protesting about, although rumours on social media suggested it was because he was about to lose his home.
St Helens Council would not confirm how the man gained access to the roof and it unclear whether a town hall investigation will now take place into the incident.