He was elected to the Greater London Council for the Wood Green division in 1973, where he was appointed chairman of the General Purposes Committee.
Although the new group was supported by the Cabinet minister Reg Prentice, who declared that he would speak in its support on "any platform", the decision to criticise mainstream Labour politicians and trade unionists – including Michael Foot and the railwaymen's leader Sid Weighell – for writing opinion pieces in Communist-backed newspapers did not go down well.
[3] Harold Wilson, speaking at the party conference that year, attacked the SDA as an "anti-party group which has been disporting itself in Blackpool this weekend, leaking… their smears to an ever-ready Tory press.
He served on the board of The American International University in London, and was a senior fellow at the Federal Trust.
Haseler published extensively, including The Gaitskellites (Macmillan, 1969), The Death of British Democracy (Elek, 1976), The Tragedy of Labour (Blackwells, Oxford, 1981), The Battle for Britain: Thatcher and the New Liberals (I.B.