Ministers have defended their plans to force the long-term unemployed to do manual work or lose benefits.
Chief Secretary to the Treasury Danny Alexander told the BBC the idea was not to "punish or humiliate" but to get people back into the habit of working.
But the Archbishop of Canterbury Rowan Williams said the changes could drive people "into a downward spiral of uncertainty, even despair".
Work and Pensions Secretary Iain Duncan Smith is to unveil the plans this week.
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 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'
Job advisers would be given powers to require tens of thousands of claimants to take part in community work for charities or local councils.
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."
The Archbishop of Canterbury, Dr Rowan Williams, expressed his concern, telling the BBC: "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 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 - and at the moment there were five people chasing each vacancy.
Mr Alexander denied the plans were treating the long-term 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.
This meant that "more people can do what they want to do which is get a job and go out to work because that is the best thing for the country, but it is also the best thing for those individuals and it is by far the best route for anybody out of poverty".
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."
Shadow Work and Pensions Secretary Douglas Alexander accused the government of "focusing on the workshy but offering nothing to the workless".
There are five unemployed people chasing every job vacancy, he said, adding: "The tragic flaw in the Tory approach is that, without work, it won't work. A longer dole queue will mean a bigger benefits bill."
Richard Exell, a senior policy officer at the Trade Union Congress, said there was high unemployment, not because of a problem with the work ethic, but because there were not enough jobs.
"Unemployed people are the victims in this story, not the villains," he said.
The UK has five million 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.