Conservative MSP John Lamont described it as "a token gesture" unless proper action is taken to tackle prison overcrowding.
He also argued that the SNP's plans to create two 'new prisons' were in fact replacements and that the third planned prison does not even yet having planning permission.
"In addition, all of these plans were inherited by the Scottish Government from the preceding Labour/Lib Dem Executive," he argued.
Lamont instead suggested the need for more police in the community, a zero-tolerance approach to drugs and effective rehabilitation services in order to cut prison numbers.
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Labour justice spokesperson Richard Baker raised concern that the rebuilding of the prisons did not seem to have any timescale or details about the funding of the projects.
He welcomed the replacement of the prisons, but suggested: "It smacks of locking the stable door after the horse has bolted. The prisons crisis is with us now and today's announcement will only provide existing capacity and not find one new place, at some unknown point in the future."
Commenting on the announcement, SNP Justice Committee member Stuart McMillan suggested it was "good news" for both Greenock and Inverness.
As for the concerns of Labour and the Conservatives, he remarked: "Opposition carping doesn't hide the fact that the pace of delivery has far outweighed their own failed records.
"The utter hypocrisy from the Tories is simply breathtaking, and their junior spokesperson is quite simply wrong. Not one single new prison opened during the 18 long years when the Tories were in power. Plenty of factories, mines and shipyards closed. Yet no prisons opened.
"Labour's response is equally incoherent. The prison population is at an all time high and rising because the SNP Government inherited it from the Labour administration. They had a chance to ease that pressure on staff with home detention curfews but abandoned this support for petty partisan reasons."
(GK/JM)
