A consortium of investors led by Criterion Capital Partners saved SeeSaw from closure in June this year after taking a majority stake in the business from previous owner, the transmission firm Arqiva.
However, Arqiva said that Criterion had failed to provide its "committed funding", meaning there was no other option remaining and SeeSaw "had to close".
A notice posted on SeeSaw's website reads: "Thanks for your support, but SeeSaw is no longer available."
Arqiva created SeeSaw after spending £8m to acquire the IPTV technology developed for Project Kangaroo - the BBC Worldwide, ITV and Channel 4 joint venture that was blocked by the Competition Commission.
SeeSaw launched in February 2010 and Arqiva invested heavily in acquiring more than 3,000 hours of on-demand programming for the site from the main UK broadcasters and overseas content providers. The site claimed to attract around 1m unique visitors a month at one stage.
However, Arqiva put the website up for sale in May after conducting a strategic review of the business, leading to the sale of a 75% stake to Criterion.
Content from Channel 4 and Channel 5 dropped off SeeSaw after Criterion struggled to lock down funding for the site from its lead backer in the investment consortium.
SeeSaw platform controller John Keeling, commercial director Matt Rennie and product director Richard Dines resigned from the company last month, intensifying speculation that the end was nigh.
In a statement issued today, Arqiva said: "Having completed the sale of SeeSaw in July, Arqiva is very disappointed by the failure of the new investors to provide their committed funding. Without that funding the service had to close."