The former Charlton boss had said it would be "an injustice if Manchester United did not win the title".
That annoyed Chelsea boss Avram Grant who voiced his disappointment over the comments.
"I will raise a glass to whoever wins the title because they will have deserved it," Curbishley re-iterated. "It is too ridiculous for words really.
"If I am supposed to be biased in favour of Manchester United, how come we've beaten them the last three times we've played them?
"United can expect no favours from us."