A baby seal has been taken into police custody after he was found loitering outside a police station.

The tiny trespasser was spotted napping beneath a car in the car park of the Wellington Police Maritime Unit at Queens Wharf in New Zealand.

Officers swooped immediately, and - with the help of a broom - managed to capture and detain the pup, who they nicknamed Steve.

Senior Sergeant Dave Houston said the car's owner had been more than a little bemused at returning to find several officers poking around beneath his vehicle - but said the young seal had had a lucky escape, as if the driver had left without noticing what was hidden beneath his car, Steve could have been killed.

"He could have been squashed," he told Stuff NZ.

While a "little bit bitey", Steve otherwise went down quietly and was kept in police custody until he could be bailed out by the Department of Conservation.

They now plan to release him back into the sea off the south coast.

According to conservation workers, the pup is at the age when mother seals tend to free them to live independently, and they can get very tired during their first few days of freedom.