Liberal Democrat deputy leader Simon Hughes has warned that the government's proposed welfare benefits cap will "break up families" and "damage the lives of literally hundreds of thousands of children."
Mr Hughes, who is not a minister and therefore not part of the coalition government, made his comments to the BBC ahead of more crucial votes in the House of Lords this week, as the Welfare Reform Bill (WRB) goes through its report stage before returning to the Commons.
On 17 January Peers are due to vote on proposals to cap the amount of benefits any family can receive at £26,000 per year. Last week, cuts that would hit the sick, the vulnerable, the disabled and terminally-ill were defeated in the Lords by three Crossbench (independent) amendments.
Lord Freud, the government minister responsible for the passage of the WRB in the Lords has been roundly criticised for trying to get the will of the House overturned by introducing a procedural amendment when most Peers had left the Chamber.
With vigorous opposition from disability campaigners, charities, civic groups, churches, medical practitioners, the TUC, public figures and parliamentarians growing, Mr Hughes told the BBC that he did not believe the Welfare Reform Bill would be passed as it stands.
The 'Spartacus Report', produced by sick and disabled people themselves, has created enormous political waves over the government's mishandling of its consultation over Disability Living Allowance (DLA), which comes back for discussion this week.
Ministers say their legislation would increase incentives for people on benefits to work while protecting the most vulnerable and saving up to £18 billion. Critics say that it will hit the sickest worst, and dispute the government's economic calculations.
Commentator and Ekklesia associate Savitri Hensman explained: "Setting aside the human cost, it is not even clear that the reforms will lower the welfare bill in the short and longer term."
She continued: "For instance, at present, if the main breadwinner of a family, whose wife is in a low-paid job, is diagnosed with cancer and becomes so ill that he can no longer work, he may have to rely on Employment and Support Allowance (ESA). Family income will drop greatly, quite apart from the anxiety and sorrow faced by both adults and children and the sick man’s pain and discomfort. Under the Welfare Reform Bill before it was amended in the House of Lords, income would probably fall still further after a year as his ESA was withdrawn, plunging the family into dire poverty."
"Whether or not the parents stayed together, the children’s educational performance and future health and employment prospects might well be affected, with long-term costs to society," she added.
"There is also an economic cost when income in the poorer groups – which tends to go quickly back into the UK economy, since most is spent on necessities – falls. If, in many localities, there is less to spend on food, clothing and so forth, shops and other businesses will sell less. In turn, if some of their workers are laid off, they will spend less, and so forth. The wealthy may accumulate savings, or even speculate with their income, so redistributing money upwards will not help the economy in the same way," said Ms Hensman
The Lib Dems' Simon Hughes told the BBC there were "bottom lines" in politics and that one was "making sure that those with least finances and the most mouths to feed, and the most needy" were protected.
He continued: "You can't penalise the families of a particular size today and say 'this must be the limit', no matter if you have one child... or four children and retrospectively say that people will have less money in the years ahead."
He said the Welfare Reform Bill was in danger "because we cannot allow families to be unjustifiably and retrospectively penalised and left with not enough money to stay in their homes and be literally forced onto the street. That is unacceptable".
Charities and NGOs are now calling for a legislative pause to allow serious reconsideration of these issues.
* The report on DLA changes written by disabled people themselves, 'Responsible Reform' is being made available online at Ekklesia and elsewhere. See: http://www.ekklesia.co.uk/responsiblereformDLA  An easy-read version has been made available by United Response: http://bit.ly/xy0elw 
* Mr Grayling, is the Welfare Reform Bill really affordable?, by Savi Hensman - http://www.ekklesia.co.uk/node/16054 
* Please wear the Spartacus twibbon: http://twibbon.com/join/spartacusreport 
* More on the Spartacus campaign: http://www.ekklesia.co.uk/spartacusreport