Speedy use of the heart-starting equipment can help boost survival rates of heart attack victims, but only one of the 26 local authorities which responded to a Freedom of Information request have the machines in all of their primary schools.
Each year, only around 5% of the 3,500 people in Scotland who undergo attempted resuscitation outside hospital for a heart attack survive to hospital discharge.
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Use of a defibrillator within 3-5 minutes of an attack can increase survival rates by up to 75%.
Scottish Liberal Democrat health spokesman Alex Cole-Hamilton said: "Our emergency services do an incredible job, but getting an ambulance to someone within five minutes to administer a defibrillator can be extremely challenging. Every second counts in a life-or-death situation and therefore it's vitally important that such equipment is available quickly.
"Earlier in the year we revealed the availability of defibrillators in secondary schools which showed Edinburgh City Council led the way in installing defibrillators in all of its secondary schools.
"Disappointingly, there is a completely different picture in Edinburgh primaries, where only one primary school out of 88 has a defibrillator installed. Other areas of the country are also seriously lagging behind, revealing a concerning picture.
"These life-saving devices should be available in schools across Scotland and we want to see councils achieve what North Ayrshire has with 100% of primary schools being equipped with a defibrillator.
"With schools being used on evenings and weekends for community-based activities, it is critical that such equipment is made available for the wider public, too."