Face of Nation : Mark Drakeford will describe how the bonds keeping the four nations together are “being torn apart by Brexit” and “couldn’t-care-less Tory governments”.
In Brighton, he will also repeat a commitment to campaign to remain in the EU in an election or fresh referendum. Mr Drakeford previously said Welsh independence was “rising up the political agenda”.
“Our task under a new UK Labour government must be to build a new United Kingdom,” he is expected to say. “One that genuinely works for its four constituent parts.”
It is the first UK Labour conference since Mr Drakeford took over as Welsh Labour leader and first minister from Carwyn Jones last December.
In his speech on Sunday, he will set out a plan to reform the union, saying it “can only be Labour that articulates a different vision for those repelled by the poisonous politics of division and despair”.
Mr Drakeford will add that through reforming the UK and remaining as part of the EU, the Labour party can offer an alternative to “narrow nationalism and worn-out imperialism”.
His stance on campaigning to remain in the EU has put him at odds with the UK Labour stance on Brexit. Labour leader Jeremy Corbyn has said if the party wins power it will offer a referendum choice between Remain and a “credible” Brexit option.