See link above. The accusation, of course, is predicated on the assumption that the Liberals did make some offers. In fact, it seems the opposite. It was Grewal who asked for a senate seat for his wife (see here), fished for a cabinet post for himself, insisted that re-election as a liberal would be easy (if a cabinet minister), and in the end announces that he would not cross because he would not have an equivalent sense of security (see p. 14, just below the middle). (This didn't stop him from asking against the next day though: here).
What does all this tell us? (Attention Reporters--this is the man-bites-dog story--The Liberals were Telling the Truth!)