The establishment was one of five which received a single star in the recent list of ratings published by Environmental Health and Pollution Regulation.
But, following another visit by inspectors on Thursday, five stars were awarded.
The one star was given after inspectors visited while work was being carried out to an upstairs storage area, said Liberation Group managing director, pubs and inns, Jayson Perfect.
A rating could not be awarded, so a default one star was given.
White D'Or manager Craig Duquemin said that the restaurant used to have its storage space below the Harbour Lights.
'Having to go right down to the bottom cellar through the pub was not ideal,' he said.
After some £30,000-worth of work, the upper room, which had not been used previously, was renovated and now houses the restaurant's freezers and stock.
Mr Duquemin said that after the rating was published, the restaurant requested a repeat visit.
This took place on Thursday and, as a result, the restaurant was upgraded immediately to five stars.
