So it's all too good to be true after all.

Of course we all knew the UK's carbon emission figures had just a passing acquaintance with reality, but now researchers at Oxford University have revealed how estranged the two are.

According to a new study, titled Too Good To Be True? The UK's Climate Change Record, the UK's official claims that emissions have fallen 15 per cent on 1990 levels are dangerously incomplete and misleading.

The headline figures look impressive but the vagaries of the official figures collation mean that emissions from shipping, aviation and perhaps most significantly imports are not included.

Take these emissions into account - and given the atmosphere does not care if the emissions appear on a balance sheet somewhere there is a strong case for including them - and far from seeing UK emissions fall they have climbed by almost a fifth since 1990.

It is slightly unfair to suggest the government has been deliberately deceiving us. All countries exclude aviation, shipping and import related emissions from their official calculations and are very open about how their figures are calculated. Moreover, the fact that the supposed fall in UK emissions is down to the shift in the energy mix from coal to gas rather than any successful green energy policy has been widely reported.

However, the study does raise an interesting question about what both governments and businesses should or should not include in their emissions reporting.

It is easy to understand the temptation to exclude as many emissions as possible from calculations, but from a risk perspective it is best to resist this temptation and include pretty much everything you can.

While it is fair to argue that the embedded carbon in imported products should be recorded by the company that manufactures the product rather than the company that buys it, other emissions external to a company's facilities, such as those from corporate travel and supply chains, should certainly be included in carbon accounts.

It is only a matter of time before a bunch of academics kick up a PR storm by undertaking a study on a major firm's emission reports that finds that, as with the UK, their figures are on the optimisitic side.

Moreover, with emission reporting standards evolving fast (witness the launch today of the Prince of Wales' Accounting for Sustainability guidelines) firms already reporting their emissions would be advised to take as conservative approach as possible.

It would be hugely embarrassing for any firm if the reporting standard that will inevitably emerge over the next five years demands that they include emissions that they had previously ignored, leading to a huge spike in their reported emissions.

It is hardly the most sophisticated piece of advice, but when it comes to corporate carbon reporting if there is any doubt about whether emissions should be included or not you are best off erring on the side of caution and sticking them in.