Members of the Welsh parliament have received "abusive and threatening messages" over the controversial 20mph speed limit rollout.
Speaking in the Senedd on Wednesday, the presiding officer Elin Jones said she was one of several members who had received such messages on social media, email and telephone "due to their stance on this topic".
Last Sunday, Wales became the first country in the UK to drop the default speed limit from 30mph to 20mph for restricted roads, in a project costing around £33m.
A petition to scrap the limit has now become the most signed on the Senedd's website since records began.
And new 20mph signs have reportedly been defaced in areas including Conwy, Gwynedd, Newport, Torfaen, Wrexham and Flintshire.
Ms Jones said: "While it's encouraging to see unprecedented interest in our petitions committee and its work, we all have a duty to ensure that public debate in Wales is measured, dignified and respectful."
The Welsh government says the change will save lives, make communities safer and save the NHS in Wales £92m a year.
Despite more than 175,000 people signing the petition calling on the government to "rescind and remove the disastrous 20mph law", Welsh First Minister Mark Drakeford said he would not be scrapping the policy and said the decision had twice been approved by parliament.
The government in Cardiff predicts up to 100 lives and 20,000 casualties will be saved in the first decade.
Not all 30mph roads will see their speed limits reduced as councils have the power to exempt certain roads from the scheme.
The Welsh Conservatives have opposed the change, with leader Andrew RT Davies previously calling the default limit an "economy-stifling vanity project".
Ms Jones said she had received representation from one member about the conduct of another member during Senedd proceedings on Tuesday.
She urged the chamber to set "the tone for how we expect others to express their views, whatever their stance on this matter or any other matter, and that we do that in a way that does not demean or undermine any individual".
"I will conclude by urging members to bear all of this in mind when articulating their views in the chamber and in turn influencing how others behave outside this chamber."