The big questions on the future of the triple lock

A sprinkling of question marks are being thrown around what in Westminster is called the "triple lock".

It is a promise that dates back to the Coalition Agreement in 2010 - when the Conservatives and Liberal Democrats came together in government.

"We will restore the earnings link for the basic state pension from April 2011, with a 'triple guarantee' that pensions are raised by the higher of earnings, prices or 2.5%," they said.

Combatting pensioner poverty and acknowledging older folk have fewer ways to increase their income was the justification.

Oh, and there is also the power of the grey vote.

Older folk are more likely to vote than young people, so if you're a politician, you mess with pensioners at your peril.

The political consequences of that promise, though, made in the scramble of five days of assembling a government in May 2010, have been - and will continue to be - long lasting.

Arguments have since raged about inter-generational fairness.

Are younger people let down by the political system, and older people prioritised?

Oh, and the triple lock is mighty expensive, not least because each year's rise is baked in.

Thirteen years on, three big questions about its future linger.

What should the government do this autumn in deciding how much the state pension should go up next April?

Up to now, when earnings have been higher than either prices or 2.5%, it is a figure representing total earnings that has been used. But the Work and Pensions Secretary Mel Stride won't commit to that.

And sources in government are letting it be known that they are contemplating something a little lower.

The argument is made that this year's total earnings figure is distorted by some one-off payments that were agreed to resolve strikes in the public sector - and a figure that discounts this would be more reasonable.

A rise of 8%, rather than 8.5%, for example, would save the Treasury hundreds of millions of pounds.

It has been argued, by folk I have spoken to in government, that there is the legal underpinning to do this.

It is the Social Security Administration Act 1992. This says "in each tax year the Secretary of State shall carry out a review of the general level of earnings in Great Britain, taking into account changes in that level which have taken place since his last review".

In other words, that you could look at earnings across the whole year, rather than the figures for May to July, which includes these extra payments.

But that is the law. And here is the politics: the convention is to use the overall earnings figure, and not doing that could be interpreted by some as breaking the spirit of the triple lock.

Neither the Conservatives nor Labour have committed to keeping the triple lock come the next general election.

Here is the bind they are both in: It is very expensive.

And some argue it is unfair to younger generations.

But it is mighty difficult for politicians to take stuff away, particularly if you fear your opponent will not.

I suspect that if the Conservatives keep it, Labour will too. If the Tories tweak it, Labour may well follow suit.

But what about the long term? That brings us to….

Enter again the Work and Pensions Secretary Mel Stride, who has told the BBC it is not sustainable in the "very, very long term".

Usually at Westminster, folk talking about the "very, very long term" mean a week on Friday. I exaggerate, but only a bit.

Politics, by its very nature, is very often very short term.

Mr Stride was actually talking decades ahead and projections from the government's official forecaster, the Office for Budget Responsibility, which point to its astronomical costs in decades to come if it is maintained.

You can hear Jonathan Cribb from the IFS talking to us about this on the latest edition of the BBC's Newscast podcast.

But Lord Hague, the former Conservative leader, wrote in The Times that the triple lock is "a very fierce sleeping dog that hates anyone to tread on its paws".

The politics of waking up that pooch, this side of the election - doing anything radical about the triple lock - looks mighty difficult for either main Westminster party.