TOKYO (Reuters) - Melco Crown Entertainment Co-Chairman James Packer said on Wednesday that it would take at least US$5 billion (S$6.3 billion) in investment for an integrated resort in Japan.

"I think realistically that would be the lowest possible number. I think the numbers will only go up from there, not down," Packer told reporters after a speech in Tokyo.

"I do not envisage that an integrated resort in either Tokyo or Osaka would be successful at anything under US$5 billion, and the cost for the successful applicant would probably be more than US$5 billion," said Packer, who controls Australian casino group Crown Resorts and is one of Australia's richest men.

Japan's parliament is preparing to debate legalising casino gambling for the first time, a move that could create a prize market for its wealthy population and proximity to China.