ZURICH (Reuters) - Prince and people are pitted head-to-head in tiny Liechtenstein on Sunday when the subjects of Hans Adam II go to the polls to decide whether to give the 300-year-old royal house more power.

Cat and pig remains left on doorsteps of the prince's critics have added a macabre twist to the proceedings, while the prince himself has vowed to leave his tiny capital Vaduz for Vienna if his proposals are not upheld.

A decade-long row over the principality's constitution will culminate with the result of the referendum that has polarized opinion among the 33,000 inhabitants of Europe's fourth smallest nation and prompted record voter turnout.

Prince Hans Adam II von und zu Liechtenstein is adamant that his suggested changes to Liechtenstein's 1921 constitution will merely legitimize his position as ruler.

However, by granting him the right to veto legislation, nominate judges and sack the government, critics argue the plans stack the deck too much in his favor and threaten to damage the principality's image abroad.

The princely house has already raised the concern of the European Commission for Democracy through Law which said Liechtenstein ran the risk of isolating itself in Europe.

But Hans Adam II and his heir Alois have held their ground, threatening to leave the country if neighboring states demand they back down.

"We would in those circumstances simply cease to be head of state," Hans Adam II said ahead of the polling, referring to himself using the royal "we."

Liechtenstein, bordered by Switzerland to the west and Austria to the east, faces a two-question ballot with a counter-proposal put forward by concerned residents of the 160-square-km (62-square-mile) country.

The prince's proposals would give him powers to veto parliamentary laws, but he would lose the right to rule by emergency decree for an unlimited time or name government officials. Voters could also choose to end the monarchy by referendum.

The counter-proposal would give the electorate the right to overrule the prince's decisions.

Observers say with the nation divided the vote will be tight. The Vaterland newspaper said on its Web Site on Saturday that voter turnout would reach record levels and that 60 percent of the electorate had already cast their vote.

"It looks like many Liechtensteiners were in a hurry to cast their ballot on constitutional reform," the paper said.