Business Green: Lobbyists campaigning against US carbon legislation may be well used to accusations of underhand tactics, but it seems that one firm has now gone too far in its attempts to torpedo the climate bill working its way through the Senate, and is now facing Congressional investigation after admitting to forging letters arguing against the bill. According to reports, Washington-based lobbying firm Bonner & Associates sent at least 12 forged letters to House Representatives in the run-up …