Colin Beattie wants other MSPs to support his motion to note concern over the decision to widen the gaps between the segments of the chocolate bar.
Toblerone manufacturer Mondelez International announced the change last week and blamed it on rising food prices.
Mr Beattie's motion calls on the UK Government to take "speedy action to rectify the change".
His motion asks: "That the Parliament notes with concern Mondelez International's recent decision to widen the gaps between the segments of the iconic Swiss chocolate bar, Toblerone, in the UK; understands that this was made in order to allay rising costs for numerous ingredients; believes that this is emblematic of the devastating consequences that Brexit could bring; offers its condolences to those mourning this change to the bar; calls on the UK Government to take speedy action to rectify the change, but wishes the company the best possible success with the lighter bar."
Scottish Conservative MSP Murdo Fraser said: "It appears that the SNP's quest to find grievance in all things has now entered the confectionery stall. What a joke.
"However, given the grief Mr Beattie is suffering over the scaling-down of Toblerone, the Scottish Conservatives pledge today to buy him some good Scots chocolate, like a pack of Tunnock's tea cakes which - regardless of Brexit - remain as delicious and substantial as always."