Labour's David Shearer says vulnerable consumers should be told the total price they will pay at the end of a lay-by purchase.

Concern has been raised over "a huge omission" in new laws which aim to protect vulnerable consumers, with Labour MPs saying poor people will still pay exorbitant prices for basic food items - including $20 for a can of baked beans.

Consumer Affairs Minister Paul Goldsmith appeared before Parliament's Commerce committee on Thursday, discussing the implementation of a suite of law reforms on consumer credit, including the Responsible Lending Code which came into force on June 6.

Labour's consumer affairs spokesman David Shearer raised the issue of mobile truck shops, which provide goods to consumers who were required to pay "exorbitant" prices for them later.

More and more of the mobile lenders were selling food, and should be banned from doing so, along with a ban on alcohol and cigarettes.

"One I came across charged $20 for a can of corned beef, $35 for a packet of noodles, $66 for a packet of powdered milk," Shearer said.

That amount was not charged because that was how much the items cost, but because consumers were subject to a "lay-by" scheme.

Shearer said it was a "huge omission" that the RLC did not require lenders to tell people the total price they would ultimately pay for items once interest rates had been added to their loan.

"If somebody is buying a good they should know what the good should cost ordinarily in a shop, and they should be given the interest rate, and with the interest rate and the term they should know exactly what they'll be paying at the very end of it.

"So for somebody buying a good thinking they're getting a good deal because they're paying per week, they may end up paying several times what that good is valued at but they never get to see that figure because this Minister decided that it wasn't relevant."

Goldsmith acknowledged at the select committee that the issue of expressing the full cost of an item paid for over a period of time should be looked at.

The important thing was to make sure people understood the cost of what they were buying and the interest they would be paying over time, which was what the Responsible Lending Code aimed to do.

The Code required that people lending to consumers checked they would not be subject to undue burden in repaying their debt.

Shearer said it showed the new legislation was already being recognised as deficient.

Truck shops only operated in poor socio-economic areas, Shearer said, and many people's desire to buy at that inflated price would be eliminated if they saw the end cost.

"These trucks go round at dinnertime and sell goods which look cheap when they are on a weekly repayment but actually total up to $20 for a can of baked beans - it's really ridiculous."

"Everybody is not very far from a dairy or a supermarket - all this is doing is preying on their vulnerability at that time."

Goldsmith said he was in no doubt that some lenders had been operating outside responsible lending principles, but added that they would be found out very quickly under the new law.

There were no plans to ban trucks going into particular suburbs or from offering food.

There was also no intention for the Government to put a cap on prices of products sold.

Shearer also raised the idea of banning certain people with a tendency to get taken in by credit schemes from purchasing from the truck shops.

New Zealand was "way behind" Australia on that, and across the ditch interest rate caps had also been introduced which just about every Western country in the world had.

Labour MP Kris Faafoi questioned whether the Commerce Commission had sufficient resources and funding to enforce the new laws protecting vulnerable consumers from unscrupulous lenders.

"It's great to have new codes, it's great to have new legislation, it's great to have new principles - but if you're not letting the people who are policing this have new tasks and new resources, how effective is it really going to be?"

Goldsmith said the Commerce Commission had adequate resources to do the job, and had played an active part in community education around the new responsible lending provisions.

"The most important part about reviewing the law is getting a good, clear set of principles that the Commerce Commission can use or enforce, so we've got good, clear law in place now, they have the legislative tools and they've assured me that they have the resources to police it, and that is very much what I'd expect of them."

* Read the Responsible Lending Code and the section on assisting borrowers to make an informed decision.