Roaming charges for using a mobile phone abroad will be abolished from December 2015 in proposals expected to be voted through the European parliament on Tuesday, but operators have warned that bills could rise domestically to pay for the change.

Posting holiday snaps to Instagram or keeping up with emails while abroad should no longer result in unexpectedly high bills under legislation to be approved by members of the European parliament's industry committee on Tuesday, which is due to be rubber stamped by the full parliament on 3 April.

Operators will no longer be able to charge travellers to the European Union's 28 member states extra for calls, texts and internet use, a practice that telecoms commissioner Neelie Kroes has described as a "cash cow" for the industry.

These charges are already set to fall from €450 (£376) per gigabyte to roam on the internet to €200 in July as a result of recent European legislation. But abolishing roaming charges completely will make a big difference for consumers – meaning they will pay the same rate as at home, currently around £10 per gigabyte in Britain. One gigabyte is just enough to download a single standard definition feature film from iTunes.

But a coalition of networks representing 45m consumers has warned that the legislation is so badly designed that the cost of domestic calls could rise to pay for it.

"There is a risk that domestic tariffs for European consumers will increase," according to the roaming coalition. "Roaming might not be subject to surcharges anymore, but the overall level of tariffs would increase, and non-roaming customers might effectively foot the bill for roaming customers."

The coalition, which represents 15 operators and virtual networks including Three, Virgin Media, France's Free and Italy's FastWeb and CoopItalia, says in order to avoid a hike in domestic call costs, the wholesale prices that operators charge rivals for customers to roam on their networks needs to come down.

Smaller operators fear they could be charged more than their customers are paying, while Europe's largest networks could do deals to limit their costs.

From July 2014, the wholesale cost of roaming will be capped at 5 cents per megabyte of data or per voice call made, and at 2 cents per text. This sounds low, but British customers currently pay less. Data costs around £10 per gigabyte for consumers, while the European wholesale cap is not set to fall below €50 or £42 per gigabyte.

"Effective wholesale regulation is key," said Three Group's regulatory affairs director John Blakemore. "Without it if customers from northern Europe go to southern Europe and use their smartphones they are going to incur very large wholesale charges, but the amount operators can recoup is going to be cut. That is unsustainable and at some point that could have an impact on the domestic prices operators have to charge their customers."

Britons and other northern Europeans are likely to be hit hardest, because they travel more and usually holiday in southern member states.

An alliance of the largest operators warned last year that abolishing roaming could cost the industry €7bn in cash flow before 2020. The European Telecommunications Network Operators' Association has claimed that removing one of the most profitable sources of revenues could force networks to slash their investment, hampering the roll out of 4G services.

The new legislation states that from 15 December 2015, consumers will be given "the confidence to stay connected when they travel in the Union without being subject to additional charges over and above the tariffs which they pay in the Member State where their contract was concluded".

The roaming coalition is hoping for an amendment before the bill passes its final hurdle this autumn, when it goes before the council of EU ministers. It wants wholesale caps to come down, and be based on the true cost to operators of providing the service.

Receiving a shockingly high bill will remain a risk for those travelling outside Europe, however, because there are no price controls. Last week Citizens Advice called on the UK's mobile phone providers to do more to tackle the growing problem. The charity said 130,000 consumers contacted it in 2013 to seek advice about unexpectedly high mobile phone bills, which in many cases are driving victims into serious debt.

• This article was amended 18 March 2014 to correct the unit of measurement. The correct unit is "gigabytes".