First Minister Carwyn Jones says the cost of spending cuts on Wales could be felt for generations.
He said Wales was facing its toughest challenge since devolution with a "devastating impact".
As he spoke, a new poll suggested 57% in Wales believe public sector cuts were being implemented unfairly.
But the Wales Office said most thought cuts were the result of "economic chaos" left by Labour and the UK government was acting in a fair manner.
Mr Jones made his comments while responding to the public sector cuts during a speech at Cardiff University.
"The UK spending review is clearly regressive," said Mr Jones. "The human and social impact could be both devastating and wasteful: the real cost could be with us for generations."
The opinion poll, carried out by YouGov for researchers at Cardiff and Aberystwyth University, also found that 53% of people believe that the cuts are unavoidable.
Some 34% of people believe that the Conservative and Lib Dem coalition government in Westminster are most to blame for the spending cuts, while 32% blame the previous Labour government.
About 3% per cent blame the Labour and Plaid administration in Wales, while 19% blame all of them.
The poll also indicates that more than 40% of people who voted Liberal Democrat at the General Election believe that Wales faces greater spending cuts than the rest of the UK.
Mr Jones said: "In real terms, they amount to a reduction of £1.8bn over the next four years, £860m of which comes out of our budget next year. This is a massive challenge.
"Our public services are critical to the fabric of our society. We have a distinct approach to public services within Wales, a cooperative model that England finds hard to emulate.
"However, the cuts will put real pressure on our ability to meet the needs of our population with the same high standards of service and care that have developed over the last 10 years."
Mr Jones also criticised the approach taken to public sector cuts in England.
A Wales Office spokesman said: "Most people recognise that cuts are unavoidable due to the economic chaos we inherited from Labour.
"That's why the coalition government, through the Comprehensive Spending Review (CSR), is taking decisive action to cut the deficit in a manner which is fair and which puts our economy on a firm footing for the long term.
"The cut in the Welsh Assembly Government's budget amounts to less than 2% a year over the CSR period - better than the UK as a whole and far better than most Whitehall departments.
"If we don't tackle the debt now we will end up paying more money in interest to foreign creditors instead of investing in public services, supporting vulnerable people, and stimulating economic growth."
Richard Wyn Jones, director of Cardiff University's Wales Governance Centre, summarised the results of the YouGov poll as "unavoidable, but economically damaging and unfair: that is how the majority of the Welsh electorate view the forthcoming cuts in public spending. "
Professor Roger Scully, director of the Institute of Welsh Politics at Aberystwyth University, said the poll showed people in Wales did not think the cuts were all the fault of the previous Labour government.
"Most people here are not convinced that it is all Labour's fault, nor are they convinced that the cuts are being implemented fairly.
"The Conservatives and Liberal Democrats have a lot of persuading to do before next May's election".