With all eyes on May's general election, Carwyn Jones condemned David Cameron's Conservatives as being even more extreme than Margaret Thatcher.
He said voters had a choice between "hope and despair".
Meanwhile Labour leader Ed Miliband has launched an attack on tax avoidance for damaging the "fabric of society".
He told the conference there would be a "root and branch" review of Her Majesty's Revenue and Customs if Labour won the election, claiming the UK's tax authority had one rule for the rich and another for the poor.
In his keynote speech on Saturday, Mr Jones hailed the Welsh government's record on jobs, investment and tuition fees as evidence of what a UK Labour government could achieve.
He said the Conservatives "denigrate" the NHS in order to dismantle it, and insisted Labour's record on health in Wales was better than that of the Westminster coalition running it in England.
Mr Jones also called for a more "tolerant" society which could debate immigration with "fairness and respect", and not let "right-wing, dog-whistling xenophobes drag us down to their level".
A Â£40m scheme with the aim of helping people set up 10,000 new businesses creating 17,000 jobs over the next five years was also announced.
Unusually for the first minister, this was a speech dominated by attacks on the Tories.
He recalled the days of his political awakening during the miners' strike and said the current cutbacks were more severe than those felt in the 1980s.
He even likened the so-called bedroom tax to the poll tax.
There was some policy but basically this was a speech that acknowledged that the next few weeks is not about his government, although the Conservatives have other ideas.
Just to pick up on one comment: he took a hard line on health boards, saying he won't apologise if they fail.
This is a change of tone and I'm told it's the result of deep frustration with Betsi Cadwaldr health board in particular over the way last week's decision to move to a midwifery-led maternity unit at Ysbyty Glan Clwyd was handled.
I think we can expect more of this tone in future, as Welsh government ministers become more open in their views of health boards if they feel there are problems.
Only Labour can stop the Tories from decimating public services, the first minister has told the Welsh Labour conference in Swansea.