A bid to allow the Welsh dragon to be legally displayed on car number plates is being made by Plaid Cymru Assembly Member Janet Ryder.
A little-known European Union regulation banning national flags being shown means that the many drivers who do so are breaking the law.
Ms Ryder claims the Government has abandoned a pledge made seven years ago to change the rules and allow national flags.
She said: "It will clarify the situation but, more importantly, it will give the right to people in Wales to display their Welsh flag on their number plates if they wish to.
"Lifting the ban on national flags would make legal what many people living in Wales are at present doing illegally".
Tory AM Brynle Williams said: "Is there anything wrong to show one's pride in being Welsh? I believe not."
Deputy First Minister Ieuan Wyn Jones urged AMs to support Ms Ryder's bid, adding that he would soon be meeting UK Transport Minister Jim Fitzpatrick to ask for the ban to repealed.
"Certainly things are moving ahead and support today would be a step in the right direction," Mr Jones said in a Senedd debate.
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