In 1901 he was elected to the Australian Senate as a Free Trader sitting for Western Australia. He had the distinction of being called to the bar in Australia, Ireland and the UK. Harney moved to England in 1906 and joined the Liberal Party. In the 1922 election he fought South Shields defeating the sitting National Liberal MP Havelock Wilson by 25 votes. He retained the seat with more comfortable majorities in 1923 and 1924 with only Labour opposition. He died a few weeks before the 1929 general election when the seat was won for Labour by James Chuter Ede.