The Liberal Party used to pride itself on constitutional conservatism, but now senior ministers are seriously proposing a constitutional amendment for no other reason than to stack the deck against same-sex marriage, writes Chris Berg.

The Australian constitution has one great feature. It is incredibly hard to change.

This, obviously, is what Scott Morrison was thinking about when he proposed last week that Australia hold a constitutional referendum to deal with same-sex marriage.

A plebiscite would simply determine the public's view on changing the Marriage Act via Parliament, but a constitutional referendum would propose adding the words "opposite and same-sex" before the word "marriage" in section 51(xxi) of the Constitution.

A plebiscite would have to simply receive a national majority to be considered decisive. But a constitutional referendum would have a much higher bar: both a national majority and majorities in at least four states.

Australia's constitutional amendment system is often described as "notoriously difficult". We are a "frozen continent", constitutionally speaking.

Only eight out of 44 referendums have succeeded. This often cited figure understates the failure rate. Other possible referendums have been abandoned before coming to a vote. Kevin Rudd dropped Julia Gillard's local government referendum when it became clear the Coalition's enthusiasm for change was waning.

The Australian founders may not have intended it to be this hard to change the constitution. But there are good reasons for constitutional change to be difficult.

Constitutions exist in order to provide fixed rules about what governments can and cannot do. The strength of a constitution derives from the certainty it provides. A constitution that can be easily changed is not a constitution at all, in that it does not offer the stability necessary for long term economic and political management. In the pre-constitutional era, governments did not feel bound by rules. Now they do. That's a very good thing.

This does not mean constitutions should be impossible to alter. But the danger to the constitution comes from reckless change, not stubborn adherence to the status quo. As Geoffrey Brennan and Hartmut Kliemt have written:

The slowness of the procedure will give us pause and help us steer a steadier constitutional and political course than we would do otherwise.

It's important to note that the desirability of constitutional rigidity holds true even if we think the constitution is weak, or flawed, or could be amended in an obvious way.

Yes, we all have our own ideas of how statutes and constitution might be rewritten that would make this country more perfect. But just have a brief scan of the previous 44 referendums (Wikipedia has a nice list, with links to the questions themselves). It is pretty clear that Australia is better off, on balance, for having rejected most of them. Almost all were outright and explicit power grabs by the Commonwealth.

With all this in mind, the requirement that a constitutional referendum achieve a double majority - majority of the population and majority in the majority of states - is in fact a relatively low bar for a change to the rules that govern the structure of the government.

After all, what is the alternative? Simple majority voting? Majority voting is not inherently more democratic.

We are more likely to make democratic decisions - that is, decisions that more represent the will of the people - with a higher threshold. When 51 per cent of the population impose their views on 49 per cent of the population, it's hard to say that imposition has much moral authority.

This is the basic case for constitutional conservatism (couched admittedly in economic terms rather than the usual legal ones). Continuity should be preferred. Change should be resisted.

The Liberal Party used to be the party of constitutional conservatism. Labor has always wanted constitutional reform. The Coalition's historical role is to hold the line, to espouse modesty and stability; the sort of virtues represented by the Samuel Griffith Society and a long line of conservative judges and political leaders.

Yet under Tony Abbott, the Coalition appears to have abandoned that storied and entirely necessary tradition.

In opposition, Abbott had signed up to Gillard's local government referendum. He had to be pulled back into line by state Liberal party divisions.

Abbott wants to amend the constitution to recognise Indigenous Australians. You only need observe how the recognition debate has spiralled out of the Government's control to see how antithetical it is to the conservative mindset.

Now senior ministers of the government are seriously proposing a constitutional amendment for no other reason than to stack the deck against a policy they oppose. And that policy is, we are repeatedly told, a second-order issue.

There's no reason for a constitutional referendum on same-sex marriage. The High Court has said the Commonwealth Parliament has the power to legislate in this area. The constitutional approach is only being floated because Morrison and others want the measure to fail.

Constitutional conservatism was once a matter of deep Liberal identity. Now it's just another political trick for short-term gain.

Chris Berg is a senior fellow with the Institute of Public Affairs and author of Liberty, Equality and Democracy and Magna Carta: the Tax Revolt that Gave us Liberty. Follow him on Twitter: @chrisberg.