Tens of thousands of protesters have marched in Budapest against a plan by the Hungarian government to tax internet use from 2015.

Tuesday's rally, the second in three days, also showed growing discontent among mostly younger citizens against Prime Minister Viktor Orban's policies centralising power and increasing the role of the state to the detriment of private enterprise.

The government has said that it is just trying to reduce the country's debt, but many Hungarians see it as an attempt to restrict their freedom.

Protest speakers outside the Ministry of Economy called on Orban to withdraw the plan to force internet service providers to pay 700 forints ($2.89) per individual subscriber and 5,000 forints ($20.65) per business subscriber every month.

Initially, the tax was set to be 150 forints ($0.62) per gigabyte of internet traffic, but Orban's ruling party, Fidesz, said it would set a cap on the levy.

The government, which announced the proposal last week before any consultations with industry groups or even Fidesz lawmakers, gave several explanations for the measure - it was meant to complement a tax on telephone calls, as people were increasingly using the internet to make calls; it would take a bite out of the telecommunications companies' allegedly large profits; and the new revenues would help improve internet access in rural areas.

Protesters vowed to continue the rallies, which were also held in several other Hungarian cities and at some Hungarian embassies in EU countries, until the government withdraws the tax plan.