Europe will ban mobile phone networks from charging customers more to use their phones abroad, according a leaked draft of legislation which the European commission will publish next week.

Neelie Kroes, the commission vice-president who speaks on digital affairs, is bent on ending the unpopular roaming fees, which have left many holidaymakers with huge bills on their return home. Her proposals have faced fierce opposition from the largest networks, including Vodafone, Orange and Telefónica, which say the end of roaming within Europe could cost them €7bn (£5.9bn).

Networks will be left with little choice but to offer a flat rate to customers at home or abroad for calls, texts and internet connections across Europe, according to a draft document seen by the Guardian. This will be achieved using airline-style alliances in countries where operators do not own a network. The alliances will have to cover at least 85% of the European population and 21 member states.

Kroes has described roaming charges as a "cash cow" for operators and "a disproportionate irritant for travellers". She aims to boost Europe's digital competitiveness with proposals for a single telecoms market which are scheduled to be endorsed by the commission on 11 September. Member states will meet next month to discuss the plan, which will also need approval by the European parliament.

A recent draft of the 93-page document promises to "guarantee common high levels of consumer protection across the union, including measures to gradually end mobile roaming surcharges".

As well as tackling call costs, the commission will use a swath of measures to create a single telecoms market, while stopping short of creating a single European telecoms regulator. There had been suggestions that powers could be taken away from national watchdogs such as Ofcom and handed to Brussels.

Other new measures include open internet safeguards to stop broadband companies blocking legal but competing websites and services such as Skype, and plans to harmonise mobile spectrum sales across the region. This is intended to avoid a repeat of the piecemeal 4G allocation.

The commission began forcing operators to cut roaming costs last year. Many charge customers extra even when they are using a local network owned by the same company as their domestic network. While Europeans cannot unknowingly run up a bill larger than €50 (£42) while abroad, roaming charges are still many times higher than domestic call costs and will remain so without further legislation.

Kroes is proposing that companies which phase out roaming from July 2014 will face lighter-touch regulation. For example, they will not be forced to offer customers a choice of providers for foreign calls.

From 2014, customers would be able to keep costs down by selecting another provider for calls, texts and internet data services while travelling, if their own network charges extra for service abroad. They could do this without having to change their phone number or buy a new sim card.

The draft rules state: "When parties to collective roaming agreements offer to all their customers by default roaming tariffs at the level of domestic tariffs, the obligation of domestic providers to enable their customers to access voice, SMS and data roaming services of any alternative roaming provider should not apply."

In the past, price caps have been used to bring down the coast of calling abroad. The last of these come into force in 2014, and after fierce resistance from the larger operators, Kroes is not proposing any more price reductions. Instead, she is hoping to force change by using incentives.

A spokesman for Kroes said: "We don't give a running commentary on the proposals but we are committed to putting in place a method that pushes roaming out of the market."