NSW prisoners called on to build cells

Prisoners will start building extra jail cells as the number of NSW inmates hits a record high.

Eighty steel modular cages will be built at prisons to hold 160 additional inmates, Attorney-General Brad Hazzard said on Thursday.

It comes after Corrective Services revealed this week that prisoner numbers had reached a record 11,100.

A spokesman said prison officers were putting extra inmates in occupied cells and "spare areas" to deal with crowding.

The Public Service Association, which represents prison officers, says capacity was reached at 10,800, and general secretary Anne Gardiner has questioned the merits of modular cells.

"I really don't think it's a feasible option for the long term," she told AAP before Mr Hazzard's announcement.

She said the best answer to overcrowding was to reopen closed sections of Grafton and Kirkconnel prisons.

Mr Hazzard said the new cells, at $75,000 each, were $125,000 cheaper than those built using traditional methods.

Prison numbers have been rising steadily during the past two years, with a seasonal spike in December pushing them to record levels.

Stricter bail conditions, introduced last week, are expected to drive inmate numbers even higher.