A Thai court on Wednesday ruled the biggest party in parliament had violated the constitution in seeking to change a law against insulting the monarchy, in what could set a precedent for any future review of one of the world's strictest lese majeste laws.

The Move Forward Party won last year's election on a progressive platform that included a once unthinkable proposal to amend the lese majeste law, which carries penalties of up to 15 years in jail for each perceived insult of Thailand's crown.

The Constitutional Court ordered Move Forward to abandon that plan, which it ruled was tantamount to an attempt to "overthrow the democratic regime of government with the king as a head of state" and therefore in violation of the constitution.