An investor in Research In Motion wants a shareholder vote on whether the company's two leaders can retain shared roles as chairmen of the board and chief executives, in the latest headwind to hit the BlackBerry maker ahead of next week's results.

The call to limit the roles held by co-founder Mike Lazaridis and Jim Balsillie adds to RIM's woes as it struggles to present itself as a legitimate third option in a smartphone race increasingly dominated by tech giants Apple and Google.

The setup makes it more difficult for the board of directors in general to ask management difficult questions, Northwest and Ethical Investments' vice-president of ethical funds, Bob Walker, told Reuters.

The proposal from Northwest and Ethical, which holds more than half a million RIM shares, calls on the company to split the roles and amend its bylaws to ensure the chair is an independent board member, RIM said in a regulatory filing on Friday.

Balsillie resigned as chairman in March 2007 and stepped down from the board in February 2009 following a stock options accounting scandal but returned, along with Lazaridis, as co-chairman in December 2010.

Northwest and Ethical said that decision contradicts the company's own statement, widely acknowledged best practice, and regulatory expectations, the filing showed.

Northern Securities analyst Sameet Kanade, who in late April wrote an open letter seeking a change in RIM's management structure, said he was not surprised by the move, but had expected it to be made by a larger shareholder.

Ideally, RIM takes proactive measures to fix an internal matter rather than a forced change such as this which further distracts focus away from a critical issue, the continual drop in market share due to lack of a competitive platform, he said.

Investors want RIM to come up with a credible response to Apple's iPhone and iPad, and to smartphones based on Google's Android operating system.

RIM said on Friday it will launch its PlayBook tablet computer -- its attempt to compete with the iPad -- outside North America within the next 30 days.

The PlayBook launched to some troubling reviews in the United States and Canada in April, amid complaints that the company had rushed the gadget to market.

RIM, based in Waterloo, Ontario, said the PlayBook will soon hit shelves in Britain, France, Germany, Australia, the United Arab Emirates and India, among other countries.

The company gave no precise dates for the international launch nor detail on price. For North America, the PlayBook matched the price tag of equivalent WiFi-only iPads, at $499 for a model with 16 gigabytes of storage, $599 for a 32 GB version and $699 for 64 GB.

But analysts warn RIM risks repeating the tepid North American start, with limited marketing clipping its potential.

RIM could have done a better job of building excitement, said Canalys analyst Tim Shepherd, who is based in England.

I doubt the average person in the street has even heard of a BlackBerry PlayBook here, he said.

RIM gave neither pricing nor exact dates for the PlayBook launch beyond North America.

RIM has already disappointed investors by slashing sales and earnings forecasts soon after revealing a weak earnings outlook.

A class action lawsuit filed last month claims RIM misled investors by not disclosing that product delays would hurt earnings.

Its shares have lost almost half their value from a February peak and sit at a two-year low. They closed 2.8 percent lower at $36.56 on Nasdaq on Friday, and down 2.3 percent at C$35.82 in Toronto.

Northwest and Ethical's Walker said the fund would have raised its concerns regardless of RIM's recent troubles.

It's a structural issue for us. Even if the share price was healthy, at this stage we'd still file this resolution, he said, adding that the fund had not yet sought support for the vote from other investors.

RIM reports first-quarter earnings next Thursday after markets close and holds its annual meeting in Waterloo on July 12.

The company called on shareholders to vote against the resolution, saying independent board member John Richardson already acts as the de facto head of the board.

It also said there was no law in the United States or Canada requiring it to separate the roles.

(Additional reporting by Euan Rocha; editing by Janet Guttsman and Rob Wilson)