By Georgina Prodhan

FRANKFURT (Reuters) - BenQ defended itself against accusations it had allowed its German mobile phone unit to go bust, saying it made every effort to save the business and even asked ex-owner Siemens for help.

BenQ Mobile filed for insolvency in Germany on Friday, putting 3,000 jobs at risk, a year after Siemens made a gift of the loss-making business to Taiwanese technology group BenQ, which previously had little experience of the handsets business.

Along with 250 million euros (7 million) of investments Siemens made in the business and 100 million euros of writedowns it swallowed before handing it over, Siemens also bequeathed to BenQ a clutch of patents and know-how.

But despite the 840 million euros BenQ said it poured into its German handsets business over the past year, BenQ Mobile continued to lose market share and finally was unable to compete against such industry giants as Nokia.

BenQ's strategy chief Rick Lei told Reuters on Friday it would have cost another billion or so to save the business, which was once the world's fourth-biggest mobile phone maker but by last quarter had just 3 percent of the global market.

"The question was: Did we have confidence we could succeed? If we'd known for sure 800 million euros would keep it alive, we'd have done it," he said in a phone interview from Taipei.

Asked why the business had failed, Lei said it had taken far longer to get new handsets to market than BenQ had anticipated, meaning the company lost money with each passing day as the phones -- especially fashion models -- became less saleable.

"The big surprise was that all the new products Siemens presented to us were delayed," said Lei, who said he was involved in the takeover negotiations. "Probably Siemens could not give us the precise information before we took over."

"We still have a certain disagreement," he added.

Lei said Siemens had turned down a last-minute request for financial help for its former handsets unit at a recent marathon meeting with "very senior Siemens management" at which they had discussed ways to save the business.

"But in the end they said: 'Business is business'" Lei said.

A Siemens spokesman declined to confirm or deny the talks but referred to comments made by Siemens' former finance chief earlier this year, in which he said he would not be surprised if BenQ came back to ask for help from Siemens.

"INCOMPREHENSIBLE INSOLVENCY"

Siemens Chief Executive Klaus Kleinfeld said in a statement on Friday: "It is incomprehensible to us that BenQ Mobile has filed for insolvency in Germany."

The company said it was examining its legal position with regard to BenQ.

In particular, Siemens said it was checking whether BenQ could still use the Siemens brand and keep the patents it got as part of the deal, given that the mobile phones business had gone under so soon after the takeover.

"The current situation does not fit with an intention of the parties to continue the handsets business in the long term," Siemens said in its statement.

Heinrich von Pierer, Siemens' chairman, defended the sale to BenQ in an interview with German daily Sueddeutsche Zeitung.

"The management didn't take the decision lightly," he said. "What tipped the decision in BenQ's favour was the assurance that it would take over the German production."

Trade union IG Metall and Juergen Ruettgers, state president of North Rhine Westphalia, said they had suspicions that BenQ had deliberately wound down the business.

On a tour of a BenQ Mobile production site at Kamp-Lintfort in North Rhine Westphalia, Ruettgers said the question had arisen as to whether BenQ had "systematically cannibalised" the German business.

BenQ's Chief Financial Officer Eric Yu responded: "We have not planned to do such things. This really is not true."

Employees at the Kamp-Lintfort plant and other German staff had agreed to work longer hours for no extra pay and to give up Christmas and other holiday bonuses in exchange for job guarantees from Siemens. Those guarantees ran out in June.

On Friday, the IG Metall union said it was investigating the possibility of legal action, possibly through a class-action case, to force Siemens to re-employ the 3,000 German staff who now stand to lose their jobs.

"It's new legal territory, but of course we will try it," Munich representative Harald Flassbeck told Reuters.

(Additional reporting by Jens Hack and Michael Able in Munich, Sheena Lee in Taipei and Matthias Inverardi in Kamp-Lintfort)