Jobseekers face losing benefits for three years under tough new rules introduced by the Government on Monday.
People who refuse to accept jobs or voluntarily leave a job without good reason have previously had their benefit stopped for three months.
Ministers said the new rules send a clear message that people receiving benefits have a responsibility to actively seek work in exchange for receiving jobseekers allowance.
Jobseekers who are ready to work hard and want to get on will get all the support they need through Jobcentre Plus and schemes such as the Work Programme, said the Government.
Last year jobcentre advisers sanctioned 495,000 claimants, including 72,000 who refused an offer of employment.
Minister for Employment Mark Hoban said: "Choosing a life on benefits when you're able to work is not an option. These rules send out a clear message to jobseekers. We will offer them the support they need to find work, but in return for receiving benefits they have responsibilities too. People cannot expect to keep their benefits if they do not hold up their end of the bargain."
There will be three levels of sanctions, ranging from four weeks for a minor offence to three years for serious repeat offenders.
"The new regime is tougher but fairer, and the rules will be clearly explained to all claimants from day one so that they are in no doubt that if they do not comply they will not get their benefit," said the Department for Work and Pensions.
Mark Serwotka, general secretary of the Public and Commercial Services union, which represents jobcentre workers, said: "Instead of punishing people for being out of work the Government should take responsibility for the pain and suffering it is causing with its failed austerity policies that we marched against at the weekend.
"With unemployment still high, there are eight people chasing every job vacancy, and many more trapped in part-time, low paid work. No one chooses a life on benefits, but some very wealthy individuals and organisations like Starbucks do choose not to pay their taxes, and they're the ones who should be demonised and pursued."