A man who emptied a bucket of faeces over a Fremantle war memorial is wanted by police.

Police have released an image of a man they want to speak to over the bizarre act of vandalism on the Monument Hill memorial about 5.30pm yesterday.

The man was witnessed by a member of the public emptying the bucket over some plaques.

When confronted, the man admitted dumping excrement on the memorial.

"That's my poo," he told the witness.

When asked why he was desecrating the memorial, he responded:"That's my personal prerogative".

The person took a photograph of the man, who appears to be carrying a guitar, and reported the incident to police.

Anyone with information is asked to contact Crime Stoppers on 1800 333 000.