Double shifts have long been a source of angst for the Australian Midwifery and Nursing Federation which started an industrial campaign against them earlier this year.

A nurse or midwife working a double shift will be on the clock for up to 18 hours - the equivalent of a blood alcohol level of .05.

The Tasmanian Health Service, ANMF and the government have been working towards a solution to the issue.

Mr Ferguson said his new policy, which will come into effect from January 18, will address the problem.

"Under the policy, a shift exceeding 12 hours will only be permissible in exceptional circumstances, when approved by the Executive Director of Nursing for the relevant region, or an appropriate delegate," he said.

The government will hire an additional 40 nurses for the Royal Hobart Hospital, 9.58 for the Launceston General Hospital and 15 additional graduate nurses in the coming months.

Labor health spokeswoman Rebecca White said the government needed to properly resource rosters to ensure there were enough nurses working each shift, or there could be terrible consequences for staff and patients.