Howarth moved to Newport RFC in 1999 and played for the club until 2003, scoring 1,035 points and helping the Black & Ambers win the WRU Principality Cup.
During the 2000 Six Nations Championship, a number of British newspapers revealed that Howarth (along with fellow player Brett Sinkinson) was ineligible to represent Wales.
However, following the revelations in March 2000, Howarth was unable to provide the documents to prove his eligibility and was subsequently not considered for selection in that season's remaining matches.
Howarth continued to play rugby for Newport RFC and in 2001 announced he intended to qualify for Wales under residency laws (which would have made him eligible again on 14 May 2002).
[3] During a 2022 interview with Sky Sport New Zealand, Howarth reiterated his belief that he was Welsh qualified, noting that he chose to represent Wales over my lucrative offers: "I can tell you now if I went to England, financially I'd have been better off.