"Sixteen kids and their teacher were murdered. Fifteen other primary school children were wounded," he added.
Local SNP depute leader and Dunblane MSP Keith Brown also criticized Lowe's rhetoric, calling it unacceptable.
He praised the legacy of the victims' families, whose efforts led to the 1997 handgun bans.
"Despite these hideous remarks from Rupert Lowe, the Snowdrop Campaign that followed ensured a ban on the private ownership of most handguns - that is the proud legacy of the bereaved families and the local community," Brown said.
Lowe launched Restore Britain as a separate political entity after his suspension from Reform UK last year.
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The Crown Prosecution Service later determined there was insufficient evidence for a conviction regarding the suspension circumstances.
