Urinating in public then defecating on police cell blankets has led to a stiff fine for a New Plymouth man.

James Sinclair Hobson, a refrigeration worker, was drunk on Devon St West at 2.15am on February 8 when he started urinating on the footpath in full view of the passing public and made no attempt to hide what he was doing.

When police arrived he ran off down Egmont St was chased and arrested on the corner of Egmont and King streets.

When searched he had a small plastic bag in his pocked containing a small amount of cannabis.

While in police custody he "excreted faeces on two blankets despite a toilet being available in the cell," the police summary says.

The soiled blankets were destroyed after it was deemed a biological hazard to put them through the wash.

In pleading guilty in the New Plymouth District Court on Wednesday to behaving in an offensive manner, intentional damage and possession of cannabis, Hobson - who represented himself - denied he had a drinking problem.

"But I did soil myself," Hobson said.

In sentencing, Judge de Ridder commented that despite Hobson's denial, it was clear he did have an alcohol problem.

Hobson was convicted and fined a total of $500 plus court costs of $390.