The company, which has been hit by a fall in advertising, said it planned efficiency savings of £155 million this year, rising to £175 million in 2010 and £245 million in 2011.
Executive chairman Michael Grade said the cuts were due to the "short-term horrors" of the economic downturn, which had seen advertising deteriorate significantly from the end of last year.
He said: "The tough actions we are taking have to be seen against that backdrop. These are unprecedented and extremely difficult times. We have to be focused more on our core business."
Mr Grade said the savings would ensure ITV is in the "best possible shape" when the recession ends.
He maintained that ITV had made "significant operational progress" over the past year, audience share was "inching upwards" and the broadcaster was increasing its advertising market share.
Drama output on ITV will be cut from eight hours a week to seven, but the broadcaster will still be investing a "huge amount" in drama, said Mr Grade.
The company reported pre-tax losses of £2.73 billion after it wrote down the value of assets on its balance sheet. Stripping out the exceptional items, profits were down 41% at £167 million.
The company also axed the payment of a final dividend to shareholders.
Gerry Morrissey, general secretary of the broadcasting workers' union Bectu, said he was "outraged" at the scale of the job cuts.
"We will do everything we can to protect our members and we will protest to Ofcom about ITV's claim to be investing more in programmes when they are cutting back.
"Michael Grade has abrogated his responsibility to ITV's staff. We desperately need a new management model."
ITV said it would not be giving any details of which programmes or other areas would be affected by the one-hour-a-week reduction in drama.
The firm has already announced it will be scaling back production of Heartbeat and The Royal, which will lead to the closure of one building at its Leeds studios.
Around 150 of the 600 job losses will be in Leeds, it was revealed.
But most of the cuts will be in London, affecting every department and accounting for around 15% of ITV's 4,500-strong workforce.
Jobs being axed include production and back office roles.
Bectu said it believed one-off drama programmes planned from this autumn would now be shelved because of the production cuts.
Changes have already been announced to The Bill, while ITV is believed to have two years of Heartbeat and The Royal episodes in stock.
The union said it believed one of the main studios in Leeds will now be mothballed, with Emmerdale being the only programme produced on the site.
It was also confirmed that ITV plans to sell Friends Reunited, little more than three years after it bought the business for an initial £120 million from founders Steve and Julie Pankhurst, the husband and wife team who set up the website in 2000.
Under the deal, first announced in December 2005, ITV was due to pay up to £55 million more this year depending on the performance of the business.
Friends Reunited delivered around half of ITV's £36 million online revenues in 2008, but saw its own revenues fall by £4 million over the year due to the loss of subscription income as the reunions site relaunched on an advertising-funded basis last May.
Martin McNulty, of online marketing agency Trafficbroker, said: "The shrink in ad revenues at ITV isn't simply the result of a global deterioration in the economy, but reflects a fundamental change in the mindset of advertisers.
"ITV's biggest competitor these days is Google and that's a major cause for concern. Increasingly, companies are switching to performance-based advertising models that remove risk entirely.
"They are demanding to pay for results rather than upfront for an advertisement that may or may not convert. At a time when every penny counts and marketing budgets have to be justified, performance-based channels such as online search and affiliate marketing can save hundreds of thousands of pounds a year."
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Bill Jamieson: ITV slump may force huge shake-up in broadcasting•
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