From Longman Dictionary of Contemporary Englisheconomical with the trutheconomical with the truthused humorously to say that someone is not telling the truth → economical
Examples from the Corpus
economical with the truth• Do not be downcast that you have been economical with the truth.• He thought I had been economical with the truth.• In insisting that no changes had been made to the original plan, his team was being economical with the truth.• In view of the Warc footnote, this statement seems to have been economical with the truth.• Members of his profession are often economical with the truth. 