Winnipeg restaurant owner Joe Chan is officially appealing a judge's decision that cleared Mayor Sam Katz in a conflict-of-interest case.

Chan lost the case last month, after Court of Queen's Bench Justice Brenda Keyser ruled that Katz did not breach Manitoba's conflict-of-interest legislation by throwing a Christmas party in 2010 for city councillors at Hu's Asian Bistro.

Katz, who owned the restaurant at the time, paid the $3,000 tab with city money.

Keyser ruled that Katz's conduct amounted to "bad political and ethical behaviour," but she believed triggering a costly election was not in the public's best interest.

The judge also ruled that Chan should pay $10,000 towards Katz's legal costs.

Chan, who owns Cathay House restaurant, said days after the ruling that he would appeal. The appeal was filed this week, his lawyer confirmed to CBC News.