A new £8m fisheries protection vessel will be too slow to keep up with most fishing boats, according to the Greens.
The vessel will be used to patrol and protect Scottish sea fisheries
The new vessel was officially commissioned by the Scottish Executive in a ceremony at Leith on Friday.
Green MSP Robin Harper said the Minna, which has a maximum speed of 14 knots, was slower than the vessel it replaces and that most boats in the North Sea would be able to outrun it.
But his allegation was denied by the executive, which said the new vessel would concentrate on inshore waters, where it would be faster than the boats it would encounter.
Mr Harper said: "More than 50% of the fishing vessels in the North Sea would be able to outrun the Minna.
"They might just as well enter a Mini into a Formula One grand prix.
"How can the executive pretend to be taking fisheries protection seriously if it commissions the equivalent of a well-equipped motorised barge to chase the much faster boats in the North Sea?
"Most of these boats are less than three years old and a high proportion are likely to have engines that have been illegally upgraded to give them a greater speed advantage."
Lower fuel use
An executive spokeswoman said: "The vessel will concentrate on inshore fisheries, where the majority of boats do a maximum 12 knots.
"The other three vessels in the fleet have a maximum speed of 18 knots, which equals the speed of the larger offshore fishing boats."
She also claimed that modern fishery protection was not about high speed chases and that the Greens should be glad that the new Minna would burn much less fuel than a high speed boat.
At the ceremony, Environment Minister Ross Finnie said: "Commissioning the third FPV Minna brings the fleet back up to four vessels and allows FPV Westra to go into well-deserved retirement after 28 years service.
"Built on the Clyde by a skilled and well-managed workforce, I anticipate the Minna will have a long and trouble-free life ot service to the monitoring and enforcement task."