A Christchurch postal worker has admitted stealing hundreds of items of mail over the last six years.

Stephen James Cadigan has been employed by New Zealand Post for 35 years.

He is now 50 and faces a warning from Christchurch District Court Judge Michael Crosbie he could get prison time at his sentencing on September 4, the Christchurch Court News website reported.

He yesterday pleaded guilty to two charges of dishonestly using documents and one of theft by a person in a special relationship.

Cadigan was a team leader in charge of the management of the branch where he worked, with responsibility for staff including posties.

Police prosecutor Sergeant Tu Maaka said Cadigan would unlock the branch first thing in the morning and spend 15 or 20 minutes alone with the mail before other staff arrived.

He has admitted he first started taking odd items of mail five or six years ago, but it was not regular and not continuous.

Over that time, he realised it was possible to steal items, and from January 1 to May 15 this year he took 20 to 30 items on most days.

He would remove valuable items such as cash, gift vouchers, or lottery tickets, and store the mail in his work locker.

The police found that over a period this year, 559 items had been opened by Cadigan. They were found in his locker.

He was apparently caught in May when he tried to buy groceries with two Pak'n Save vouchers and cash.

He admitted the thefts.

"He said he felt terrible and was still struggling to find a reason for the thefts," Sergeant Maaka said.

Judge Crosbie agreed to the request from defence counsel Carol Morgan for a report on Cadigan's suitability for home detention.

But he said that granting Cadigan bail and ordering the report was not an indication of the outcome.

"In view of the type of offending and the nature of the charges, you should expect a sentence of imprisonment, but all options will be open to the judge."