Rule No. 1: Don't lie to the media.
Rules 2-10: Don't lie to the media.
Journalists have access to a printing press. A broadcast signal. A website. Social media. And, when wronged, reporters will not hesitate a moment to use them. Especially if reporters are lied to.
Nothing says this better than the article at the following link, courtesy of PR entrepreneur Peter Shankman:
Lesson: if you're a PR person and your client asks you to lie, hand him/her your phone. Ask the client to do the fibbing. Maybe his reputation can handle it. Yours can't.