Telco iPrimus has launched what it claims is Australia's first capped-price mobile broadband service that slows the connection speed when the 6GB of monthly data allowance is reached.

The iPrimus Speedster plan starts at 6GB for $39.95 per month with a free modem being offered on a 24-month contract as a special for September.

When a customer's monthly data allowance is reached, the connection is rate shaped for the remainder of the monthly billing period and the charging meter is stopped, according to iPrimus.

At the beginning of the next monthly billing period, the access speed is restored and the data meter reset.

iPrimus believes a capped plan alleviates customers' concerns about excessive download charges.

Primus Australia CEO Ravi Bhatia said consumers want the freedom to be online at any time and existing mobile broadband pricing packages potentially risk excessive and unexpected download charges, often amounting to several hundred dollars in a month.

General manager of products and marketing at iPrimus Andrew Sims said in the company’s experience 6GB of data allowance per month is “more than sufficient for an average Internet user”.

“If a customer requires additional data in a given month, it can be easily purchased via their account toolbox so there are no surprises on their bill at the end of the month," Sims said.

"For customers that need a little more data allowance, we are also offering a 12GB plan, which is the highest data allowance offered by any service provider for this product in Australia."