Vonage Holdings filed for an initial public offering that seeks to raise up to $250 million for the fast-growing, but unprofitable Internet telephony provider. The company also named a new chief executive.

The Holmdel, N.J., company, which has raised more than $650 million in private funding, has been exploring an IPO or potential sale for several months. Details about the number of shares to be offered or an estimated price range weren’t disclosed in its filing with the Securities and Exchange Commission.

Vonage said Mike Snyder will take over February 27 as chief executive from founder Jeffrey Citron, who will remain chairman of the board. Mr. Snyder joins Vonage from ADT, a provider of security systems and unit of Tyco International, where he has been president since 1997.

Vonage has grown rapidly since it first began offering its service in 2002 and now serves more than 1.4 million customers. It charges $24.99 a month for unlimited local and long-distance calling in America and Canada. Internet-based calling is a fast-growing threat to traditional phone companies because it is less expensive than conventional service and often includes features that aren’t available with traditional service, like letting the customer choose any area code. It works by breaking voices into bits of digital data that travel over the Internet and are reassembled into sounds on the receiving end.

Vonage has spent heavily to market its service and is one of the biggest advertisers on the Internet. Its IPO prospectus shows that the company spent $213.77 on marketing for each new subscriber, while its average monthly cost to provide telephone service was $8.31 per line for the nine months ended September 30.

In that period, the company had a net loss of $189.6 million on revenue of $174 million. Marketing expenses alone were $176.3 million in those nine months and the company said it plans to continue to spend heavily on marketing and postpone profitability.