Sitting across from me in a grungy Melbourne cafe five years ago was a rising star of the Labor Party.

Our conversation turned to a notorious "branch stacker", coincidentally a factional ally of my cafe companion.

"He’s not a branch stacker," the now federal parliamentarian said as a smile crept across their face. "We call them multiple recruitment specialists."

We both laughed at what appeared to be a cute play on the old line that one person’s terrorist was another person’s freedom fighter. And so it is with branch stacking.

For many Labor insiders the role of "multiple recruitment specialists" has been a running joke for decades. But with Adem Somyurek's sacking from Victoria's ministry on Monday, the party is now paying a price for its failure to crack down on membership rorts.

So what is branch stacking? And why does it happen?

What is branch stacking and why is it a problem?

The line between being adept at recruiting – a perfectly legitimate activity in politics – and being a branch stacker can often be blurry.

Sometimes the reference to "stackers" can have racist undertones, impugning anyone who is active in politics from a non-Anglo-Celtic background.

But at the heart of the problem is people having their memberships paid for by others and having them vote in particular ways to influence preselection ballots and the like.

These types of practice are against Labor Party rules.

For decades, branch stacking has been a problem in Labor. There have been numerous internal Labor Party reviews over the years, including from former prime minister Bob Hawke and former NSW premier Neville Wran.

Other party luminaries such as the late former Victorian premier John Cain campaigned against the practice, while Bill Shorten, early in his time as federal leader, was a strong advocate of party reform.

Nothing substantial came from all that and so the problem has persisted. Warlords such as the late George Seitz have used their numbers to manipulate preselections and party processes.

In more recent times, Somyurek has emerged as a key figure in the internal workings of the party, as an investigation by The Age has so graphically shown.

Why does it happen?

One reason is that it is relatively easy. The days of political parties having large, engaged memberships are long gone.

The major parties have been hollowed out and so the numbers of people needed to control a branch or influence preselections can be relatively small. One senior Labor source estimated two-thirds of the party’s 16,000 members in Victoria may be "stacks".

The Victorian Liberal Party, before the last state election, faced problems of its own after the mass recruitment of religious conservatives, in particular Mormons and evangelicals.

The emphasis on fringe social issues among the new recruits no doubt contributed to perceptions of the Liberal Party – which lost in a landslide – being out of touch.

In Labor the factional system is far more formal than in the Liberal Party, with affiliated unions having an important say over preselections and policy. Two of the key interest groups in deciding these issues are warlords, who control numbers through stacking, and affiliated unions.

Individual party members – due to both a lack of internal democracy and clout – rarely have much influence. This becomes a vicious cycle. Why join a party where you have little role or no influence? That, in turn, can further hollow out the party and its membership.

How has paying for memberships become an issue?

To control hundreds, or even thousands, of party members requires money – often tens of thousands of dollars a year to pay for party memberships. That’s where things get particularly murky.

How former minister Somyurek paid for all the thousands of members he reportedly controlled is, so far, not entirely clear. It is almost certain he did not pay for them himself.

In other branch stacking scandals, union-linked slush funds have often been used. Money might be raised from a fundraiser or from businesses and then diverted into an off-the-books slush fund or bank account that can be raided to pay for party memberships.

Businesspeople, often from the same migrant community as the stacker, can also provide backing.

It can create insidious and murky networks of patronage and power – and almost perfect conditions for the flourishing of corruption.

Would new rules ensure genuine membership help?

It is no doubt important but may not, in itself, be enough.

Having a party more open to the views and wishes of ordinary members could encourage a more representative party and make it harder to manipulate and stack.

Labor has made some changes to become more democratic, such as the involvement of rank-and-file members in electing party leaders (decided by a 50/50 split between MPs and ordinary members).

But there are concerns from some that more internal democracy can make a party unelectable.

Many in Labor are alarmed by the experience in Britain, where Labour Party members, who have far more say than here, elected Jeremy Corbyn, their most left-wing leader in decades.

Making things harder is the decline of Labor’s traditional base.

When union members made up half the workforce, the experience of Labor-affiliated unions and their members was typical of much of the country.

Now the labour movement is in its weakest state in decades, with members concentrated in a less representative group of industries and sectors. Having more members drawn to the party or more unionists may not in itself make the party more representative of the broader community.

Beyond more democracy, it is clear the Labor Party needs more oversight of how it is run.

In previous branch stacking scandals, the party would appoint a reliable figure from the Right and Left factions. They’d write a report that would dish out some slaps on the wrist and maybe take action against some mid-level operatives. Things would quickly move on and the cycle would repeat.

But it is a big step for a political party to open itself up to more external scrutiny. Is this scandal a trigger for major change?

Maybe the scrutiny of Victoria Police and the Independent Broad-based Anti-corruption Commission into Somyurek's conduct will put a halt on the branch stacking, for now.

But that won't last forever.

The world will move on and without lasting reform to the party's internal democracy and oversight, there's little doubt this will happen again; just with a new group of warlords in charge.

It's what's been happening for decades.