Australians are being warned about so-called “shrinkflation” among the nation’s top telecommunications companies, with new figures revealing providers are capping mobile internet speeds without lowering prices.

Comparison firm WhistleOut has analysed more than a dozen mobile data plans and has found Telstra, Optus and smaller providers have unveiled speed caps over the past nine months.

Almost half of the providers are capping the speed of some or all of their plans, WhistleOut’s Joel Gibson said, labelling it “shrinkflation” – which is when products are made worse or smaller without the price changing.

“Why do airlines have first class and business class? So they can charge rich people more,” Mr Gibson said on Thursday.

“Telcos have seen the opportunity to create a sort of ‘first class’ for mobile plans, which means they can charge more – and that’s fine for those who can afford it or who need top speeds.

“But make sure you’re not still paying a first-class price for a plan that’s been downgraded to economy.”

Mr Gibson said the days where Australians could merely look at mobile plans based on the price and how much data is included may be over.

Speed has now become a new variable to consider, with Optus chief Kelly Bayer Rosmarin saying recently that telcos are trying to recoup the enormous costs associated with investing in the 5G network.

WhistleOut found 4G plans were being capped at 100Mbps, while 5G plans run up to 250Mbps.

Although these speeds are still much faster than standard NBN plans, the comparison firm said many of the speed caps haven’t been clearly advertised or explained to customers.

Mr Gibson said customers could save by downgrading to a plan with a lower speed cap if they don’t think they need excess mobile data speeds.

“You could save by downgrading to a plan capped at 100Mbps, which is still as fast as a typical Fast NBN plan and twice as fast as the most common NBN plan,” he said.