The tiny principality of Liechtenstein has been rattled by a war of words between activists who want to revoke the royal veto and the hereditary prince, who has threatened to quit if they do.

Liechtenstein owes its very existence as a principality to its royal family and their princes, who have ruled it as an autonomous monarchy since the dissolution of the Holy Roman Empire in 1806.

But the current ruler, Hereditary Prince Alois von und zu Liechtenstein, has threatened that his 900-year-old family will drop its royal duties if Liechtenstein passes a referendum eliminating the prince's veto, a power enshrined in the constitution.

"The royal family is not willing to undertake its political responsibilities unless the prince... has the necessary tools at his disposal," Alois said in a speech to parliament on March 1.

"But if the people are no longer open to that, then the royal family will not want to undertake its political responsibilities and... will completely withdraw from political life."

With some 36,000 inhabitants and a surface area of 160.5 square kilometres (62 square miles), the bucolic monarchy sandwiched between Austria and Switzerland enjoys one of the highest living standards in the world thanks to its industrial and financial sectors.

Long considered a tax haven, Liechtenstein has an average annual income of $137,070 (104,062 euros), according to the World Bank -- the second-highest per capita in the world after Monaco.

Alois' father Hans-Adam II, who transferred sovereignty to his eldest son in 2004 but officially remains head of state, is worth nearly $4.0 billion, according to Forbes magazine.

But the family, which still lives in its ancestral castle towering over the capital Vaduz has run into an attack on its power in the form of a petition drive dubbed "Yes, for your voice to count".

The slogan refers to plans by a citizens' committee to launch a referendum that would repeal the prince's veto power.

The movement first gained steam last year, when Alois, a 43-year-old father of four, threatened to veto a referendum legalising abortion if citizens passed it.

After an acrimonious campaign, the referendum failed. Proponents blamed the prince's veto threat.

"The referendum was doomed to fail," Sigvard Wohlwend, a spokesman for the movement, told AFP. He said the veto threat had "torpedoed" its chances in a monarchy where the royal family is still treated with reverence.

Wohlwend, who said the current campaign grew out of the abortion referendum, insisted the activists' goal is not to do away with the monarchy but to give more power to Liechtenstein's people.

But it is an uphill battle.

The campaign must gather 1,500 signatures by May 10 to call a referendum -- not so easy in the fourth-smallest country in Europe, after the Vatican, Monaco and San Marino.

"It's like a village here, and everyone knows everyone else. People don't want anyone to know they're voting for the referendum," Wohlwend said.

Campaigners are trying to assuage residents' fears.

"The prince would retain all his rights and the monarchy would remain in place," Paul Vogt, a committee member, explained in the local press.

Wilfried Marxer, a political scientist and director of the Liechtenstein Institute, said other small states such as San Marino manage to survive without monarchies.

But in Liechtenstein, he said, the monarchy is a "deeply anchored tradition".

"People are afraid they would lose their identity and their quality of life if the monarchy disappeared," he said.

On top of that, "The prince has not shown any willingness to compromise," he added.

A final obstacle: even if the referendum passed, the prince would have the power to veto it -- though analysts say it's more likely he would resign his duties and retire from politics.