Speaking at a Wales Governance Centre event in the Pierhead, he will warn that the way the nations of the UK work together will need to change if the union is to survive.
Two years ago the Welsh Government published ‘Brexit and Devolution’, a plan to address the implications of Brexit for the devolution settlement, intergovernmental relations, and the UK constitution.
As things currently stand we will leave the EU on 31 October, potentially in a catastrophic no deal scenario.
We are likely facing a straight choice between a no deal Brexit or remaining in the EU – and we are unequivocal in backing remain. To make this happen, we are calling on Parliament to legislate for a referendum, with remain on the ballot paper.
It is my view that a disorderly, chaotic exit from the EU would threaten the very future of the United Kingdom, and no amount of reform of the current intergovernmental relations will be capable of mitigating that risk.
In future, the devolved administrations must be fully involved in negotiating our future relationships. We need to see concrete progress and an undertaking that compromise will be needed on all sides. In that way, we have a chance of delivering change.
There have been successes, and there are encouraging signs across Whitehall that the penny is beginning to drop. Welsh Government will continue to lead the debate, and to make the case for a set of intergovernmental structures which meet the challenges we face now, and will face in the coming years.
When we published Brexit and Devolution, we didn’t claim to have all the answers. We said: here are the issues we face as a result of Brexit - the reasons why the existing intergovernmental machinery simply won’t cut it anymore. And here are our proposals for change.
Two years on, what’s changed? The short answer is not enough.
Today, people under 40 can barely imagine a world without devolution, but in many ways the UK Government’s approach still reflects a very dated ‘grace and favour’ attitude: if we behave ourselves, the UK Government will, out of the goodness of its hearts, allow us some limited powers of self-government.
The existing, inadequate intergovernmental arrangements and structures remain, without even an agreed plan for how they might be reformed. In that sense, nothing has changed. No progress has been made in respect of our call for a Council of Ministers, or for a better system for dispute resolution. And that is deeply disappointing.
If we are to see real progress, we need a change in attitude towards devolution, based on mutual respect and parity of esteem and participation between the various governments.