Long-term benefit claimants could be forced to do manual labour under proposals to be outlined by Work and Pensions Secretary Iain Duncan Smith.
He is due to outline plans for four-week placements doing jobs like gardening and litter clearing.
He said the message would be: "Play ball or it's going to be difficult."
But the Archbishop of Canterbury warned that the planned welfare changes could drive people "into a downward spiral of uncertainty, even despair".
Under the plan, claimants thought to need "experience of the habits and routines of working life" could be put on 30-hour-a-week placements.
Anyone refusing to take part or failing to turn up on time to work could have their £65 Jobseekers' Allowance stopped for at least three months.
The Work Activity scheme is said to be designed to flush out claimants who have opted for a life on benefits or are doing undeclared jobs on the side.
'Bit more of a push'
Reports suggest it will target people believed to be sabotaging efforts to get them back into work.
Foreign Secretary William Hague told the BBC's Andrew Marr Show tackling the welfare budget was "one of the big political challenges".
"What we are talking about here is people who have not been used to working having both the opportunity and perhaps a bit more of a push as well, to experience the workplace from time to time and again the vast majority of people in Britain will think that's the right thing to do."
The white paper will set out Mr Duncan Smith's plans for a universal credit to replace the range of benefits currently claimed by the jobless.
Under the scheme, job advisers would be given powers to require tens of thousands of claimants to take part in community work for charities or local councils.
A Department for Work and Pensions spokesman said: "We will shortly be bringing forward further proposals on how to break the cycle of dependency blighting many of our communities and make sure work always pays."
'Cycle of dependency'
Mr Duncan Smith said his plans were designed to reduce welfare dependency and make work pay.
He said: "One thing we can do is pull people in to do one or two weeks' manual work - turn up at 9am and leave at 5pm, to give people a sense of work, but also when we think they're doing other work.
"The message will go across; play ball or it's going to be difficult."
Danny Alexander, Lib Dem Chief Secretary to the Treasury, denied the plans were treating the longterm unemployed in the same way as criminals doing community service, telling the BBC's Politics Show the "purpose is emphatically not to punish and it's not to humiliate".
It was intended to "support and encourage" and to get people back into the habit of getting up and going out to work. It also meant those who did it could demonstrate their employability to prospective employers.
The UK has 5m people on out-of-work benefits and one of the highest rates of workless households in Europe, with 1.9m children living in homes where no-one has a job.
The Archbishop of Canterbury, Dr Rowan Williams, expressed his concern about the proposed changes, saying: "People who are struggling to find work and struggling to find a secure future are - I think - driven further into a downward spiral of uncertainty, even despair, when the pressure is on in that way.
"People often are in this starting place, not because they're wicked, stupid or lazy, but because their circumstances are against them, they've failed to break through into something and to drive that spiral deeper - as I say - does feel a great problem."
Deputy Labour leader Harriet Harman told the Andrew Marr Show she would have to wait to see the full details of the proposals on Thursday before giving her verdict.
But she said the government needed to understand that to get people back into work, there had to be jobs for them to go to.
She added that Labour would be voting in the Commons on Tuesday against plans to cut Housing Benefit.