Prince Philip was legally a knight for more than a fortnight before Tony Abbott revealed his captain's call to the country on Australia Day.

The Prime Minister's office first sought advice about giving the Queen's husband a knighthood in November 2014, Department of Prime Minister and Cabinet officials confirmed on Monday.

Prime Minister Tony Abbott's decision to make Prince Philip an Australian knight has been widely ridiculed. Credit:Samir Hussein

They also revealed the Letters Patent for the Order of Australia had to be amended because the Duke of Edinburgh was not an Australian citizen, making him an "honorary" knight only.

It was also necessary to place Prince Philip ahead of Prince Charles in the order of precedence.