Some climate change sceptics have been guilty of applying double standards in their condemnation of alleged misdeeds by researchers at the Climatic Research Unit at the University of East Anglia.

On 25 February, I wrote to Dr Benny Peiser, the director of the Global Warming Policy Foundation which is chaired by Lord Lawson, to warn him that a graph of "21st century global mean temperature" displayed prominently on his group's website contains an error.

Instead of showing that 2009 was the warmest year since 2005, the foundation's graph portrays it as slightly cooler than 2006 and 2007.

While it is a relatively small error, it is the kind of discrepancy that many sceptics would be seizing upon if it had been found on the website of the Climatic Research Unit.

Yet Peiser still has not responded to me and the foundation's graph still remains inaccurate. And it is not the first such error.

When the foundation first launched its website in late November 2009, I wrote to Peiser to point out that his graph mistakenly showed 2003 instead of 2005 as the warmest year of the new century. He replied, acknowledging the error and stating that the graph was intended to represent the HADCRUT3 data series that is compiled by the Met Office's Hadley Centre and the Climatic Research Unit at the University of East Anglia.

The foundation corrected the error a few weeks later. When pressed, Peiser told journalists that "a graphic designer" was to blame for the problem and insisted that the graph was just "a logo".

Now that the foundation's "logo" has been updated to include a data point for 2009, it has introduced a new misrepresentation of the data compiled by the Met Office and the University of East Anglia.

I have also asked Peiser if Professor Ian Plimer, who is a member of the foundation's "academic advisory council", was involved in the preparation of the dodgy graph. Plimer's recent book, which is promoted heavily as a "reference work" by sceptics, contains a figure which also misrepresents the HADCRUT3 data series.

Yet the inaccurate portrayal of global temperature since 2001 is not the most misleading feature of the foundation's graph. It is the fact that it excludes the entire temperature record from the 20th century, and thus the marked increase that has taken place such that nine of the 10 warmest years on record have all occurred in the last decade.

What makes this attempt to "hide the rise" all the more ironic is the fact that the foundation has been so keen to highlight one of the emails, sent in November 1999 by Professor Phil Jones, which includes the phrase "hide the decline".

As is now well known, this phrase was referring to the practice of adding the instrumental temperatures since the 1960s to a proxy record compiled from tree rings that erroneously indicated a cooling over the last four decades of the 20th century.

In his written submission to the current inquiry into the emails by the House of Commons Science and Technology Committee, the foundation's chairman, Lord Lawson, described the practice as demonstrating "a lack of integrity". Lord Lawson repeated this accusation on 1 March when he and Peiser represented the only pressure group invited by the committee to give oral evidence.

We are still waiting to see how Lord Lawson explains his foundation's misleading and inaccurate portrayal of the temperature record compiled by the Met Office and the University of East Anglia.

Bob Ward is policy and communications director of the Grantham Research Institute on Climate Change and the Environment at London School of Economics and Political Science.