First recorded by Argent (1970).
Hit version by Three Dog Night (US #7/CAN #4/AUS #72 1971).
From the wiki: “‘Liar’ wasg written by Russ Ballard (‘Winning‘, ‘Since You Been Gone‘) of Argent from their 1970 self-titled debut album. It was released as the band’s first single, but did not chart.
“A version by Three Dog Night was released the following year and featured on the band’s album, Naturally.”