It is, according to people burnt by auto renewal on car insurance, like Tesco bringing you the same bag of shopping next week unless you ring them to say you don’t want it.

Readers are furious about huge hikes in premiums pushed through by insurers using a continuous payment authority they unwittingly signed up to when taking out their car cover the year before.

One told us of a bank that charged £340 for a new-ish Ford Focus in Norfolk, but then took £700 the following year under auto renewal. The driver had seen the renewal notice but ignored it and bought a separate policy (costing £350) by going to a comparison site. The new policy came from the same bank that had tried to charge her the £700 as an existing customer. It then tried to charge her £150 to cancel the other policy.

Another reader in Sussex told us he explicitly rang the insurance company to cancel a policy, but still had £415 taken from him. He insists he had never agreed to the continuous payment authority. He was then hit by a £40 cancellation fee.

Gripes about auto renewal are not new – the Financial Ombudsman Service says it receives around 500 complaints a year. But judging from the recent flow of letters into Guardian Money, perhaps a number of insurers are now taking things too far.

Insurance companies say they always remind buyers beforehand and give them time to cancel. They add that auto renewal is welcomed by many busy people who don’t have the time or inclination to shop around, and would hate to find themselves illegally uninsured at the end of their cover.

But we have also seen instances where insurance firms mask auto renewal – for example, writing about “the benefits of staying with us” without explicitly making it clear the customer is entering into a longer term contract. We’d like to know if auto renewal is turning into a fiddle to bump up premiums or charge cancellation fees.