The BBC has apologised and said that it "should have challenged" claims made by politician Lord Nigel Lawson contesting evidence about climate change.

The former Chancellor of the Exchequer spoke on the broadcaster's Today programme in August and referred to the UN's Intergovernmental Panel on Climate Change as he claimed that there had been "no increase in extreme weather events" and that "mean global temperature has slightly declined" in the last years.

The statements were followed by complaints from some viewers.

According to reports in the Guardian, a letter has now been issued by the BBC's executive complaints unit that "now accepts the interview breached its guidelines on accuracy and impartiality".

The publication quoted the letter stating that Lord Lawson's statements "were, at the least, contestable and should have been challenged".

Colin Tregear, the BBC complaints director, said: “I hope you’ll accept my apologies, on behalf of the BBC, for the breach of editorial standards you identified.”

A spokeswoman for the broadcaster said that the latter comment referred to the content of Lord Lawson's claims and added that there were other guests present on the programme that offered "different views".

The Global Warming Policy Forum, a London-based campaign group chaired by Lord Lawson, later said on Twitter that his information was "erroneous".

Simon Bullock of Friends of the Earth said: “It was a real choke-on-cornflakes interview, with Lord Lawson’s misleading climate denial views given undue weight and passing unchallenged. After this ruling hopefully the BBC will now move the climate debate on to how to stop our planet warming, not denying that it is happening.”