West emerged as a fierce critic of the negotiations that would lead to the Sunningdale Agreement, and led the "anti-White Paper" Unionists in the Northern Ireland Assembly, 1973.

Powell stood for and won the South Down constituency in the October 1974 general election, but his opposition to the restoration of Stormont and preference for greater integration with the United Kingdom was to cause ruptures within the party.

The UUUC lasted another few years and won the overwhelming majority of the seats in the 1975 Northern Ireland Constitutional Convention which sought to gain consensus on the future of the province.

He remained active in the Ulster Unionists for some years and was the party's unsuccessful candidate in the bitter April 1981 by-election in Fermanagh and South Tyrone caused by the death of the sitting MP Frank Maguire, West received 29,046 votes and was defeated by Bobby Sands standing on an Anti-H-Block/Armagh Political Prisoner ticket with 30,493 votes; Sands died twenty-six days after his election.

Afterwards West remained a member of the Ulster Unionist Council and was highly critical of his successor, James Molyneaux, for his opposition to proposals for power sharing devolution.