It was the verbal punch-up of the year so far, the debate between former Labor minister and Sky News presenter Graham Richardson and former Labor leader and ­occasional Sky News panellist Mark Latham on Paul Murray Live last Monday night.

Some leftist critics bang on about how the pay-TV channel has low ratings when compared with free-to-air channels such as the ABC. Others, including journalist Paul Bon­giorno, want to bar Sky News being shown at airports and on airlines at certain times. But the fact is debates on Sky News frequently dominate ­national news coverage, including on the public broadcaster.

The Richardson-Latham clash fired up when the former bagged the latter for appearing on robo-calls in the Longman by-election campaign in Queensland sponsored by Pauline Hanson’s One Nation. Latham urged voters to support minor parties and criticised Labor leader Bill Shorten.

Richardson said Latham was a “rat” — an allegation soon up­graded to a “king rat”. In turn, Latham accused Richardson of all sorts of alleged misdeeds in and outside the Labor Party — some going back four decades or so. Meanwhile, Murray presented as a mild-mannered referee who was not inclined to interrupt the bout.

The use of the word rat in political debate is as old as the century-old Labor Party. It was traced by John Iremonger in a chapter ­titled Rats in the book True ­Believers, edited by Labor true ­believers John Faulkner and Stuart Macintyre in 2001. The term was used to describe a one-time Labor member who left the party and became one of its opponents.

In his emotive essay, Iremonger used the words rat, rats, ratting and ratted to dismiss anyone who had once joined the ALP but chose to leave and disagree with its policies or practices. In Iremonger’s view, Labor had properly adopted a position that depicted all who abandon it as apostates. Political hatred runs deep in the ALP.

In other words, ALP member Richardson accused former member Latham of the most mortal sin in Labor secular political commandments. Richardson was consciously linking Latham with Billy Hughes, Joe Lyons and Jack Lang as well as Frank Mc­Manus, Jack Kane and Vince Gair.

The term rat in Labor’s word usage goes to an individual’s veracity and honesty. Yet of the six “rats” listed above, all but Lang left the ALP on a matter of perceived principle. Moreover, Hughes and Lyons led non-Labor parties to electoral success on a total of six occasions and neither led their new party to defeat at the polls. Of Australia’s 29 prime ministers, Hughes and Lyons rate fifth and six in terms of years served.

Hughes was prime minister in 1916 when the First Australian Imperial Force was ­engaged in military action on the Western Front against the German army. He wanted to reinforce the AIF by introducing conscription for overseas service. Following his failure to win the first conscription plebiscite, Hughes left the ALP and continued as prime minister with the support of what were then termed the Liberal parliamentary groups.

The argument as to whether Australia should have introduced conscription between 1914 and 1918 has continued for a century. Hughes took a decision that he ­believed was in Australia’s nat­ional interest, even though his tactic to reinforce the AIF did not prevail in the 1916 and 1917 plebiscites. In November 1918 he was the leader of a victorious nation. Hardly the attributes of a rat.

Lyons was a Labor premier in Tasmania who moved into federal politics at the 1929 election, which Labor won — under the leadership of James Scullin — on the eve of the Depression. Lyons held senior posts in the Scullin government but resigned when treasurer Ted Theodore returned to the cabinet, having stood down over allegations of corruption.

Lyons and four other ALP members left the party in March 1931, primarily over the direction of economics, and joined the ­Nationalist opposition. They opposed Theodore’s expansionary policies. Lyons later led the newly formed United Australia Party to victory in the December 1931 election and remained in ­office as prime minister until his death in April 1939. Lyons was a successful leader in the 1930s as Australia recovered from the Depression at a faster rate than in the US under Franklin Roosevelt’s presidency. Like ­Hughes, Lyons left the ALP over a difference in policy.

The same was true of Mc­Manus in Victoria, Kane in NSW and Gair in Queensland at the time of the Labor Split in the mid-50s. Labor’s erratic leader, Bert Evatt, was primarily responsible for the split, which began when he attacked the Victorian ALP’s state executive.

The dispute was primarily over the proper response to communist influence in the broad labour movement. Most of those who left or were expelled from the ALP in Victoria and Queensland were Catholics who shared BA Santamaria’s anti-communism. Once again, the term rat was used concerning those who ended up in the Democratic Labor Party — ­including Santamaria, even though he was never a member of the ALP or the DLP.

Then there was one-time NSW premier Lang who, along with some supporters, entered federal politics. What became Lang Labor was involved in the defeat of the Scullin government on the floor of parliament in 1931. When a member of the breakaway Lang Labor Party in the lead-up to the 1949 election, Lang viciously attacked incumbent Labor prime minister Ben Chifley.

Unlike the other so-called Labor rats, Lang’s disagreements with Labor were born of spite and prejudice. He was a bully and an anti-Semite. Yet, of all those who split with the ALP, Lang was the only one to be de-ratted, so to speak. He was welcomed back into the fold by a young Paul Keating in 1971.

Judging from the Sky News ­exchange, Richardson is unlikely to “de-rat” Latham any time soon.