Wales' First Minister has described Boris Johnson as "the bottom of the barrel".
Mark Drakeford made a speech at the annual Aneurin Bevan Memorial Lecture, hosted by the Aneurin Bevan Society, on Monday evening in Westminster.
In it, he continued his vocal criticism of the UK Government.
Speaking of the failure to continue the £20 Universal Credit uplift, the First Minister said: "The Cameron and Osborne era saw the poorest bear the greatest burden of austerity, with benefits frozen and children forced into the front line of welfare cuts in child benefit and the despicable family cap.
"We might have thought that the bottom of the barrel had been scraped, but we had not reckoned with Boris Johnson. The recent £20 cut in weekly Universal Credit is the single most savage reduction in benefit support for more than 70 years."
He spoke of the 2019 General Election result where the Conservatives won a majority of 80 seats in Westminster but in three of the four nations of the UK, the election was won by other parties.
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He said people may have expected "some humility" from Mr Johnson in that context of the result.
"A sense that the best thing to do would be to work closely with others in parts of the United Kingdom where its own mandate was much weaker. A sense even of needing to tread a little carefully. To ensure that a voluntary association of four nations could be preserved through consent. Through delivery of the tangible benefits of being part of a larger political, economic and social union.
"You might have thought so but the reality turned out to be quite the opposite. The dominant strain – not the only strain, but the dominant one - in the first majority Conservative Government since devolution has been, for nearly two years, determined and aggressive unilateralism.
"Their theory is plain to see devolution has undermined the United Kingdom, it has placed too much power and too much prominence in the hands of opponents with which they do not agree; successive UK Governments have been too placatory in the face of the ungrateful and ever-demanding subsidy junkies of the Celtic fringe – and it is time to demonstrate who is boss. It’s what I describe as the ‘show them’ playbook."
He posed the question: "How do we save the union?".
"First we must recognise that the Union means different things to different people. It’s why ‘muscular unionism’ - imposing a specific Anglo-centric form of the Union on British people - fails spectacularly as a unifying strategy. Rather than uniting people, it alienates those who hitherto have felt British, but not ‘this kind’ of British. The proposals of the Cabinet Office’s ‘Union Directorate’ to strengthen British patriotism – which often appear to revolve primarily around better branding and ‘flag mania’ – often risk overlooking the regional variations of the British identity.
"They seem to think that each nation’s desire for greater decision-making and greater control over their daily lives can be addressed through facile, top-down proposals for new branding or by shouting even louder about the crumbs that are benevolently handed out.
"It seems to believe that the increase in both the size and number of Union flags plastered on vaccine vials or face masks or used as official wallpaper, will convince people of the value of the Union. In short, it won’t."
Mr Drakeford said: "Only Labour can save the Union. Only a Labour Party prepared to make a progressive and collaborative case for a modern, four-nation union, can give it any chance of a viable and sustainable future.
"I do believe that the need to make the case for the United Kingdom is ever more urgent."
Again, Mr Drakeford said that devolution is at risk due to the Conservative Government.
"What the election of the first working-majority Conservative Government since 1999 demonstrates, however, is just how vulnerable the devolution settlement that has allowed these things has been to continuous attack by the Tories.
"The next Labour Government must entrench devolution, putting the settlement beyond the unilateral ability of a hostile Conservative Party to reverse the arrangements endorsed in two Welsh referendums.
"Decisions which affect only people who live in Wales should be made only by people who live in Wales. That principle is breached daily by the present UK Government."
Mr Drakeford said he hoped reform of the House of Lords will be a pledge from Labour at the next General Election replacing it with a Chamber of the Union guaranteeing representation from the nations and regions of the UK and with a make-up which genuinely reflects the voting preferences of the population.
"Of course there is a wider programme of reform which I cannot cover this evening. It will be for the Gordon Brown commission, which Keir Starmer has instigated to make those proposals, drawing on the work which we have set in hand in the Welsh context and to be led by Dr Rowan Williams and Professor Laura McAllister.
"There can be no hesitation that radical reform must be the agenda of the next UK Labour Government. No doubt it will face the call that reform has always had to face, that other matters are more urgent."
He also called for electoral reform.
"In Scotland, in December 2019, the Liberal Democrats took 9% of the vote and won four seats. Labour took 19% of the vote and won just a single seat. Nearly two out of every ten votes cast leads to one out of 59 seats won.
I have every sort of democratic quarrel with such a system, but for today I feel certain that its continuation will only feed further the fissures which threaten to prise the United Kingdom apart."