It's not that Mr Morrison should be pilloried for failing to answer - although it's not unfair to expect a prime minister to know some everyday measures of cost of living. The larger problem is one that is emerging for the government and opposition: each lack answers to the growing problem of rising costs for households.

In fact, they seem to be walking blind into a campaign where rising costs for non-discretionary items will be a deciding factor for voters' choices on election day.

Here's the issue. Cost of living measures are rising, driven largely by a 32 per cent increase in the cost of petrol, and COVID-disrupted supply chains. Add to this the prospect of possible interest rate rises this year, and household budgets could be under further strain.

New analysis in The Canberra Times today shows the impact that projected interest rate rises will have by the end of 2023 for mortgagees with the big four banks. The increase is $800 in monthly repayments for borrowers with the ANZ in NSW, and with an average loan size in that state ($779,770).

That's an outlier, but the less extreme examples are still sobering. For the ACT, the increases range between $359 and $601 in additional mortgage repayment costs per month. That will add a lot of pressure on individuals and families.

This would be a problem long in the making. Supply constraints for prospective home buyers, combined with a surge in demand throughout 2021, have led people to saddle themselves with mortgages that will weigh heavily on them when rates increase. The direction of house prices after the first few rate rises will say much about the sustainability of those mortgages.

All of this points to the need for parties to offer solutions on the campaign trail.

Many of the causes of cost of living rises, such as global oil price hikes, are largely out of the control of the federal government. Global supply chain disruptions are also beyond its power to stop, although it can and should make sure that items get to where they're needed once they arrive in Australian ports.

Labor has talked about lifting wages growth with efforts to improve productivity. That's a welcome start to the conversation, but it needs to continue.

One policy for parties to consider is support in the form of tax rebates to help households manage cost of living rises. These would have to be targeted carefully at the people most impacted by price increases. Importantly, the cost of non-discretionary items (bread, rent, electricity and healthcare) is rising faster than for discretionary items (like restaurant meals and holidays). People whose budgets are more dominated by non-discretionary items - that is, lower income groups - should get the most help.

A long-term solution to housing affordability is also necessary. Even if prices rise more slowly, or dip, cost of living pressures will make it harder to save for a home. Greater coordination between local, state and federal governments - such as through intergovernmental panels - to lift supply could put affordable home ownership within greater reach for many people. If solutions to cost of living problems and housing affordability don't come soon, voters can be forgiven for thinking they're not being listened to.

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