Ian Brock, 31, was caught on CCTV pulling his trousers down and defecating in a corner.
He then smeared his own excrement on the walls and threw a lump of it at the camera.
Brock, of Rectory Road, Llangwm, pleaded guilty to causing criminal damage when he appeared before Haverfordwest Magistrates Court on Tuesday (October 4).
Prosecutor Vaughan Pritchard-Jones said Brock had been arrested for an unrelated matter and was “highly intoxicated” when he carried out the dirty protest.
“In interview, he admitted what he had done and said he was disgusted with himself,” said Mr Pritchard-Jones.