Members of the congregation at Gunwalloe's church were shocked to find broken bottles and cigarette ends had been left scattered around the building.
The litter was found in St Winwalloe Church at Church Cove at lunchtime on Saturday, the day after an alleged rave involving 100 people had taken place at the beach.
Now church leaders are warning that people must respect the building, or they will be forced to lock it.
Carol Tarling, who until recently was PCC secretary of the church for 20 years, said: "We are very reluctant to lock the church - we don't like the church locked. We like it to be open and for people to come to the church and use it as a place of worship. We just ask that people who do go there treat it with respect."
She added that fishermen often used the church building as shelter overnight. Prayers had been said during the Sunday service, in the hope that the people who had left the litter come to terms with what they had done.
The night before, a rave was said to have taken place at the cove. Police confirmed that they had received a call at around midnight on Friday, complaining about the noise, and that officers had been sent to investigate.
PC Baxter Provan, police spokesman, said that police had also visited the area on the Saturday evening, after hearing that there was due to be a second gathering that night, but on investigation they found nothing to be happening.
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