Sendo and Ericsson had been discussing the licensing

Ericsson said it had "no choice" but to take the legal action in Germany, the Netherlands and the UK as Sendo had not signed a licensing agreement with it.

The Swedish firm is seeking damages and an injunction against sales and marketing of Sendo phones.

Sendo's chief executive Hugh Brogan said the firm was prepared to pay a "fair" and "reasonable" royalty.

Sendo had previously made a complaint to the European Competition Commission about the way Ericsson sets licensing rates for unaffiliated companies, he told BBC News.

Action 'unprovoked'

Sendo is a small player in the global market. It sold about five million handsets in 2004 compared with total global mobile sales of about 684 million.

We do not want a free ride. We respect other people's intellectual property Hugh Brogan, Sendo chief

Ericsson's case concerns alleged infringement of its GSM and GPRS handset patents.

Mr Brogan, who founded Birmingham-based Sendo in 1999, said the company had been in negotiations with Ericsson about the technology in question.

The legal action was "unprovoked and unnecessary" and took Sendo by surprise, he added.

"We do not want a free ride," Mr Brogan said.

"We respect other people's intellectual property. We will pay a fair, reasonable and non-discriminatory royalty."

It is not the first time Sendo has found itself up against one of the titans of the tech sector.

Last September, Sendo and Microsoft settled a lawsuit in which Sendo accused the software maker of stealing its technology and customers.