Last week, Dan Byles MP asked energy minister John Hayes about shale gas - his question was very specific and received a reasonable response.
Dan Byles: To ask the Secretary of State for Energy and Climate Change what recent estimate he has made of the potential size of domestic UK shale gas reserves; and if he will make a statement. 
Mr Hayes: A British Geological Survey study in 2010 estimated that if UK shales were similar to those in the USA they could yield some 150 billion cubic metres of gas, equivalent to roughly two years of UK demand.
This prompted the following tweet from Zac Goldsmith
Shale: if UK levels are similar to US, if we get it all & with no planning probs: that = just 2yrs of UK demand (Govt)
Which was instantly taken up by Roger Harrabin:
Now there was me thinking that we had lots of shale gas deposits. Worth checking out, wouldn't you think?
In fact John Hayes alluded to the possibility that there is a lot more gas out there in the rest of his answer:
The BGS has been undertaking more detailed work which also takes into account last year's drilling results of Cuadrilla in Lancashire. BGS expect to be able to publish revised estimates of the resource, that is, the amount of gas in the rocks, towards the end of the year.
However, little drilling has taken place and commercial potential of shale gas has not been quantified , so it is not yet possible to make a reliable estimate of recoverable reserves, that is, the amount of gas which might be economically producible from the resource.
So, as you see, the 2 years' supply figure predates Cuadrilla's recent drilling in Lancashire. The latest figures for onshore amount to 60-70 years' supply at current demand levels, with several hundred years' worth offshore. Now, of course, not all of that will be economic to extract, but even if only ten percent is worth the effort, it's hard to see how it's credible to characterise the UK's gas resources as "meagre". And as technology develops, that characterisation will look even worse.