The answer he gave (which didn't cover the second part of the question) was that DECC don't know what the right price is. Their stance is, in effect, "let the market decide, both domestically and internationally/globally". Perhaps another frog in hot water? (see footnote below)
This illustrates what I believe to be one of the major risks humanity faces when it comes to sustainability. The techologies, the new or alternative economics and the ideas about social adjustments exist that could solve many of the sustainability problems around energy, water, food and so on, globally and forever. The barriers to their widespread use are largely political and economic in an international context where we face the ultimate Trajedy of the Commons.
What I'd like to see is a world where these Commons are managed sustainably by global government (or by agreement between all significant resource-using nations) AND the sustainably usable products of these commons are shared equitably (but this does not mean equally) between the peoples around the world (geographically and demographically) so that poverty, starvation and other related suffering become a thing of the past. We have the knowledge to be able to do all these things, but we currently lack the political will and international agreement to do them.
The likely unsustainable crash into planetary limits is, for humanity, no less significant a threat than that of global
nuclear war, but it is perhaps an even more dangerous threat because it is more insidious and difficult to identify for the man in the street caught up in the middle of it. Many, many people are like the proverbial frog sitting in a pan of water - many are going to sit there (either denying the scale of the problems or unaware of their impact) until the water boils and it's too late to jump out (or to put the fire out).
Footnote
As a scientific footnote on the apochryphal "boiling frog" story - there seem to be conflicting reports on whether or not a frog would actually jump out of a slowly heating pan. However, it serves as a good metaphor for the real , observed effect of lack of responses to a slowly worsening situation. Perhaps, for the scientifically robust among you, you might prefer a version of boiling frog metaphor combined with the age-old saying "out of the frying pan, into the fire" ...