July 16 (Reuters) - Medical device maker Masimo Corp said on Tuesday it has filed a lawsuit against Politan Capital in a California federal court, seeking to force the activist investor to correct "material misstatements and omissions" in its proxy materials.

Quentin Koffey-owned Politan has long criticized Masimo's capital allocation and board oversight and expressed concerns about the California-based company's $1 billion purchase of consumer audio products maker Sound United.

Politan has a near 9% stake in Masimo and has nominated two candidates to be elected to the company's five-member board. Only two board seats will be voted on this year.

It is the second time in two years that Politan has proposed board candidates. Last year, Masimo shareholders elected Politan's two suggested directors, including Koffey.

Politan said there were "no misstatements" and the lawsuit by Masimo was "completely without merit".

Earlier in the day, Masimo had postponed its annual shareholder meeting to Sept. 19 from July 25.

The activist investment firm criticized Masimo's decision to delay the meeting, calling it a "last-gasp attempt" to prevent shareholder voices from being heard.

Politan said it will take all necessary actions to ensure the annual meeting is not delayed further.

Masimo's stock price has fallen 27% in the past 52 weeks. Politan has said it would immediately review strategy, costs and plans for growth if its candidates are elected.

Proxy advisory firms ISS and Glass Lewis have recommended Masimo's shareholders should vote for Politan's candidates - William Jellison and Darlene Solomon. (Reporting by Surbhi Misra and Bhanvi Satija in Bengaluru; Editing by Rashmi Aich and Krishna Chandra Eluri)