Spanish regulators have opened an investigation into the country's three largest mobile firms over allegations of price fixing.

The National Competition Commission is looking at whether Movistar, Vodafone and Orange colluded in increasing tariffs in March. The price increases were introduced after a system that rounded up call lengths to their nearest minute was banned.

By billing calls to the nearest minute instead of the nearest second, the operators raked in additional revenues of €1.21bn ($1.7bn) in 2005, according to estimates by the Spain's Consumer and Users Organisation, Reuters reports. The investigation by the National Competition Commission follows a complaint by the consumer association back in February, when the tarriff changes were introduced.

Movistar is Spain's biggest mobile operator with 22m clients. Vodafone numbers 14.6m clients, while third place Orange has 11.1m to its name. ®

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