There is a stark choice before us: on the one hand we have a new vision for Britain, on the other nothing less than the break-up of the United Kingdom. We cannot allow this important debate to be dominated by the SNP. Likewise, it cannot be addressed by a "Little England" mentality which seeks to build walls around the Tory heartland. That is why I've called for a convention to debate a new constitutional settlement for Britain. This is not just overdue, but is now a political and constitutional imperative.

In 1997, the example of Scotland helped give the people of Wales the confidence to vote "yes". Since then, both countries have made devolution work to the benefit of our people. A Welsh Labour government led the way by introducing free prescriptions, and free bus travel for pensioners and disabled people, while Scotland found a more generous approach to student tuition fees.

We have learned from each other, adapting policies to suit our own situations – delivering different approaches to meet our respective needs and aspirations. Wales does not need independence to follow a progressive path. However, devolution has to deliver, and the UK government must play its part, if we are to remain a constitutional entity. In Whitehall, devolution has for too long been viewed as a sideshow, a distraction. However, as we are now witnessing, this approach has failed spectacularly. Old certainties are being shaken by the independence debate in Scotland. I believe a constitutional convention will allow us to begin to redefine a modern UK and to reshape the context in which we all co-exist.There should now be an open debate about how the UK might function more responsively to the needs of its constituent nations. It must consider all options. I don't want the UK to break up into different parts, but it is better we consider this possibility now and not in two years' time. You can't just take Scotland out and expect the UK to continue as before.

One option could be for the House of Commons to be balanced by a new upper house with equal representation from England, Wales, Northern Ireland and Scotland. This newly shaped Lords would be similar to the Senate in the United States. I realise this would move us to a more federal structure, but it would allow full and equal representation of the individual nations.

However, this re-definition and re-shaping is not just the responsibility of the government, parliament and the devolved nations. There is a heavy onus now on the fourth estate too. The coverage of the regions in the London-based media is woefully inadequate.

Lip-service is often paid to informing and educating readers, listeners and viewers as to what devolution is and what it means to constituent parts of the UK. But health and education stories, for example, emanating from London, almost always ignore the fact that Wales, Scotland and Northern Ireland have their own control over what happens in those devolved areas of responsibility. Even after a decade of devolution, an unwillingness to accept our "differences" prevails.

If the media don't respect, reflect and report on a devolved UK, is it any wonder that the break-up of our country is now being debated? I believe it's time for us all to lay our cards on the table. We need to accept that devolution is here to stay and will, in all likelihood, deepen in the years ahead. This is not a reason to fear and retreat – this is a reason to celebrate. However, this can only be done through the auspices of a constitutional convention.

The time has arrived for the UK as a whole to define itself. Only then can we move forward to the satisfaction of all our people and secure the modern and dynamic state we deserve.