(Reuters) - Conservative Prime Minister Tony Abbott has awarded Australia's highest honor to Prince Philip, husband of Queen Elizabeth, sparking a barrage of criticism across the country on its national day of celebration.

Prince Philip was made a Knight of the Order of Australia, awarded as part of the country's honors system announced on Australia Day, with Abbott saying it paid "tribute to an extraordinary life of service.”

The award grated with republicans who want to sever ties with Britain and appoint an Australian president.

"It's a time warp where we're giving knighthoods to English royalty," Opposition leader Bill Shorten told Australian radio.

Commentator and associate editor of the national daily, The Australian, Chris Kenny tweeted, "Just another own goal and an embarrassment for Australia on our national day.” Australia is a constitutional monarchy, with the British monarch its head of state who acts in predominately a ceremonial manner but has the power to approve the abolition of parliament, which happened in 1975 toppling the then government.

Australians also questioned the procedure for issuing knighthoods, which are awarded solely on the recommendation of the prime minister to the queen. Any Australian can nominate a fellow citizen for other honors. Abbott's surprise reintroduction of knights and dames in the country's honors system last year drew criticism that he was out of touch with national sentiment. At the time he said they were intended to recognize "pre-eminent Australians.”

Abbott, whose popularity has fallen sharply in recent months, said he stood by the decision to award the knighthood to 93-year-old Prince Philip because "the monarchy has been an important part of Australia's life since 1788.”