In 1966, Batt ran as the Labor candidate for Denison in the 1966 federal election, although he was unsuccessful, with the incumbent Liberal candidate, Adrian Gibson, retaining the seat. Batt was elected to the Tasmanian House of Assembly on 10 May 1969 at the 1969 state election, representing Denison for the Labor Party. On 3 May 1972, Batt was appointed Chief Secretary and Minister for Transport in Eric Reece's cabinet. On 17 April 1974, he was made Minister for Education, with Recreation, the Arts and Federal Affairs being added to his portfolio in 1976. When Doug Lowe became Premier of Tasmania on 1 December 1977, Batt was appointed Deputy Premier and Treasurer. He was re-elected for Denison at the 1979 state election, but the enforcement of a previously-ignored rule which capped campaign expenditure at $1,500 saw the election of three MHAs declared invalid. As a result, a by-election was called for February 1980, and all Denison candidates were up for re-election, including Batt who stood down as Deputy Premier and Treasurer until the by-election was held. The ALP held a conference to endorse its candidates for the by-election, and the party's Left faction decided to produce a "how-to-vote" card, endorsing its preferred candidate John Green first, with Batt placed fourth. With the Left faction's perceived snub to Batt, the government sought to negate the effect of the how-to-vote ticket, and settled on the introduction of "Robson Rotation", a method of printing ballot papers in batches with candidates listed differently to combat the effect of the "donkey vote". Batt resumed his role as Deputy Premier and Treasurer on 25 February, with responsibility for Finance and Forests. However, on 28 July, Batt announced his resignation from the House of Assembly and the Labor Party to take up a position with the United Nations in Bangladesh. Upon the end of his UN posting, Batt worked in private industry, but returned to politics in 1986, when he was re-elected to the House of Assembly for Denison on at the state election on 8 February. On 19 February, he became leader of the Labor Party in Tasmania, serving as Leader of the Opposition until 14 December 1988. He retired from politics on 13 May 1989.
