HISTORICALLY, political defections in Britain have tended to go from left to right.

Beyond individual renegades, there are two significant markers: Ramsay MacDonald’s decision to split Labour and form a national government in 1931 and the departure of right-wing Labour MPs to the SDP (now the Lib Dems) in the early 1980s.

The 1930s also offered two further examples of significant splits. The first was Oswald Mosley’s New Party, which led to fascism. The second was the Independent Labour Party (ILP), which tried to recreate an independent socialist presence outside of Labour but was unable to do so.

Keir Starmer seems to have reversed the process, welcoming three Tory MPs to Labour, the latest being the hard-right Natalie Elphicke. However, before Tony Blair won in 1997, Tory MPs Alan Howarth and Shaun Woodward had defected to Labour.

Elphicke’s controversial move has reopened a discussion about whether the Labour Party is “a broad church” — and if so, what kind of one. Even Lord Kinnock has noted that there are limits.

When the Labour Representation Committee was formed in 1900 it certainly was a broad church. The plan was to secure parliamentary representation for working-class interests.

It was composed of trade union officers, many of whom had supported the Liberals, the ethical socialists of the ILP, the Marxists of the Social Democratic Federation (SDF) and the Fabians. The SDF mostly dropped out, and by 1918 Sidney and Beatrice Webb had drawn up a Labour Party constitution that allowed for individual membership and local party organisation.

However, after the formation of the Communist Party of Great Britain (CPGB) in 1920, the question of how broad Labour was remained open.

While applications from the CPGB to join Labour were rebuffed, there were on occasion joint Labour and CPGB candidates at elections. The communist Shapurji Saklatvala was elected as an MP for Battersea on this basis in 1922. However, by the late 1920s, the possibility of CPGB members being part of a Labour broad church was closed off.

The decades that followed saw the policing of the boundaries of Labour to the left. In the late 1930s, Nye Bevan and Stafford Cripps were temporarily excluded for pursuing a united front against fascism. In the early 1960s, Michael Foot lost the Labour whip on the issue of nuclear disarmament.

In recent decades the boundaries of the broad church have continued to be flexible and disputed. A new left around Jeremy Corbyn, Diane Abbott, John McDonnell and others built considerable influence and was tolerated by New Labour, but not in the main by Starmer who has constructed a narrow church.

He told the Observer on May 6 that everyone was welcome, but self-evidently only if they were singing from precisely the same hymn sheet as Starmer himself.

This poses a long-considered alternative question. If the Labour broad church is not that broad, can another one be built? While this applies to a wider socialist movement, the focus has often been on parliamentary success for candidates of a socialist and left-wing persuasion.

Willie Gallacher was Communist MP for West Fife between 1935 and 1950. Decades later George Galloway, himself excluded from Labour, was elected as a Respect MP for Bethnal Green in 2005. Caroline Lucas has sat as the Green MP for Brighton Pavilion since 2010.

The benchmark for those standing in an election to the left of Labour has historically been not just a hope of electoral success but that the process of being a candidate helps to build the wider movement. From time to time the question becomes whether that might see an alternative to the Labour Party appear.

It is certainly a question that Starmer’s Great Moving Right Show provokes, even if an answer will take time to appear.

Keith Flett is a socialist historian. Follow him on X @kmflett.