The UK is "riven" as a result of the EU referendum, according to the leader of the country's biggest trade union.
Len McCluskey, general secretary of Unite, is expected to tell the union's policy conference in Brighton: "I can never recall the supreme policy-making body of our union convening in such turbulent times, and with such a weight of responsibility upon its shoulders."
Jobs were in jeopardy, and long-established rights could be under threat, he will warn.
"We must condemn with all the force we can muster the disgusting upsurge of racist attacks on migrants and black Britons alike undertaken by racists emboldened by the referendum result."
Mr McCluskey will address the split in the Labour Party, saying the movement was divided - "bitterly and unnecessarily".
Mr McCluskey has been trying to heal the rift between Labour MPs and leader Jeremy Corbyn.
But a planned meeting in Brighton on Sunday between union leaders and Labour figures was called off by deputy leader Tom Watson.
Mr McCluskey issued a hard hitting statement which said: "When the possibility of a workable plan had never seemed closer, Tom Watson's actions can only look like an act of sabotage fraught with peril for the future of the Labour Party."
The Unite leader will hit out at the Government for passing the controversial Trade Union Act, which places fresh restrictions on union strike ballots.
He will say: "They are not attacking us because we are weak, but because we are still too strong for their liking. There is a trend in Toryism which will never rest until free trade unionism is virtually destroyed in our country.
"The Trade Union Bill pandered to these worst instincts. There was absolutely no public clamour for the Bill, which simply threw together the anti-union wish list of every adolescent Thatcherite on secondment to a right-wing think tank."