Interviewed by the Lauantaiseura YLE current affairs programme, Luhtanen said the number of inmates could be reduced through various means, including the repatriation of foreign nationals.
Finland has a prison population of 4,000, out of which 300 are foreign nationals.
Luhtanen does not regard the number of foreign-born inmates large, but says overcrowding can be eased by more actively returning foreign inmates to their own countries to serve out their sentences.
"At present, we send Estonians to their home country to serve out their sentences. The next-largest group is the Russians, whose repatriation is difficult because Finland doesn't have a repatriation agreement with Russia," Luhtanen said.
The governor of Turku remand prison, Juhani Järvi, says that prison overcrowding has resulted in increased aggressiveness among inmates and fatigue among prison wardens.
The Justice Ministry attributes the quick rise in the number of inmates to tougher sentences. For example, in certain crime categories fines have been raised considerably. Consequently, more people leave the fines unpaid and serve time in prison.