Budget Responsibility and National Audit Bill [HL]

My Lords, the noble Lord, Lord Higgins, has referred to Amendment 27 in the name of my noble friend Lord Peston and myself. The amendment itself says: "““In any report on the sustainability of the public finances, ‘sustainability’ must be defined””." I have tried hard to obtain some kind of definition of ““sustainability”” in the sense in which the Minister has used it—I have tried to elicit information on many of the words that he has used, as he knows—but that word, in some of the contexts that it is used, is a little difficult, to say the least. That is why we tabled the amendment; we need to know what is being talked about here. Again, I have tried to be helpful and brief. I would like the Minister to explain briefly what is meant by ““sustainability””.