Did i dream that our constitution says one parliament can't bind another?

[meandjulio]

In which case, how can the chancellor outsource decisions on levels of public spending to a non parliamentary quango forever?

I'm not an expert, and this is based on an ancient law degree...

We don't have a constitution, but 'one parliament can't bind another' comes from parliamentary supremacy law - the 'bind' is any prevention of future parliaments to act against it. Problems would come if the new law said 'and this cannot be repealed'. It's kind of like the fixed term parliaments thing - apparently it's 'fixed' but if they wanted to break the rules, they could just repeal it. Frankly I think it's populist fluff and showmanship, but never mind...

I think no Parliament can make a law that another can't decide to overturn - info here.

So presumably subsequent legislation could abolish the quango and allow for overspending.

Just for clarity, decisions on levels of public spending are NOT being outsourced. The level of public spending will still be decided by the government. The OBR will assess whether the government is complying with the requirement to run a budget surplus unless the economy is in recession.

And, as other posters have said, a subsequent parliament can repeal any law.

There is an element of showmanship here. Osborne is trying to create problems for Labour. If they don't sign up to this the Tories will be able to say that Labour still don't care about the safety of public finances and can't be trusted with the economy. But the left of the Labour party is opposed to fiscal prudence so will be very unhappy if Labour do sign up to this.

It is a piece of spin, really, as any parliament can repeal any piece of legislation (or pass it). Parliaments cannot bind future parliaments.

Even if Parliament in its wisdom decided to abolish itself, it couldn't ensure that this was permanent - future parliaments could still be formed.