LONDON  The British government on Wednesday unveiled the country’s steepest public spending cuts in more than 60 years, reducing costs in government departments by an average of 19 percent, sharply curtailing welfare benefits, raising the retirement age to 66 by 2020 and eliminating hundreds of thousands of public sector jobs in an effort to bring down the bloated budget deficit.

“Today is the day when Britain steps back from the brink,” a confident George Osborne, who as chancellor of the Exchequer is Britain’s top finance minister, told the House of Commons. “To back down now and abandon our plans would be the road to economic ruin.”

Wednesday’s announcement of £83 billion, about $130 billion, in cuts by 2015 represents a big political gamble for Britain’s fledgling Conservative-led coalition government.

Britain’s public deficit is one of the highest among developed economies, running at 11.5 percent of total economic output, compared with 10.7 percent for the United States and 5.4 percent for Germany. Though the Conservatives have so far made a persuasive case for the deep cuts, outmaneuvering a weakened Labour opposition, the country has yet to feel anything like the pain that is to come as the retrenchment begins to take hold.