Black market prices for tobacco in prisons have hit $500 for a 30g pouch - five times the price of the most prized caviar available in New Zealand.

A Herald on Sunday source said prisoners at Mt Eden Prison were paying up to $15 for a single roll-up cigarette.

Prison officials intercepted two parcels of tobacco that had been sewn into a pair of slippers and people have been trying to hurl cigarettes over prison walls.

The price of contraband tobacco has doubled since the smoking ban was implemented in July. It now costs five times the amount of Caviar Osetra, which can be bought at wholesale markets for $92 per 100g.

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Despite this, Corrections said the smoking ban introduced on July 1 was a success. In July and August, 353 contraband items were found in prisons and 31 inmates were caught smoking.

Corrections spent nearly $236,000 on staff training, books and smoke-free signage, documents released under the Official Information Act show. Nearly $5000 was spent on quit smoking books.

The amount spent annually on nicotine replacement therapy for prisoners increased from $100,000 to nearly $1 million in the year leading up to the ban.

Last month staff at Christchurch Women's Prison noticed a pair of slippers were unusually heavy, felt hard and had a strange smell.

On opening the lining, staff found approximately 50g of tobacco in each slipper plus packs of tissues.

In another case, a 20-year-old man was trying to lob a sock full of cannabis, tobacco, lighters and lollies over a fence at New Plymouth Prison on Wednesday afternoon.