John Crewe Offley's father was a noted Whig, serving as Sheriff of Staffordshire in 1679-80 and being involved in a legal incident in 1685 with Sir Robert Cotton, 1st Baronet.
Despite these difficulties, his loyalty to the Whig party was apparent; he opposed the Tack legislation in November 1704 and was blacklisted for supporting the Lords' amendments to a bill concerning the abjuration oath in 1703.
In 1705, Offley shifted focus from Newcastle-under-Lyme to Cheshire, winning a county seat alongside another Whig, Langham Booth.
However, the Earl of Sunderland recognized Offley's victory as a Whig gain, which was reflected in his voting patterns in Parliament.
During the 1709-10 sessions, Offley became involved in debates over the Weaver navigation bill, aligning against it due to potential impacts on the family's salt interests in Nantwich.