Bias is best guaged from what stories the news outlets decide not to run as well as how they approach the ones they do.
The BBC was found to be the most pro-government news outlet (in Britain) over the Iraq war - they relied more heavily than the rest on uncorroborated government-supplied information. The BBC was indeed accused of being 'anti-government' and there were resignations over a story which has turned out to be very substantive but not entirely proven. The government put out a dossier which claimed that Iraq could launch missile strikes on British interests in 45 minutes. The BBC reporter Andrew Gilligan met with the security services' chief weapons expert Dr David Kelly and later reported that the 45 minute claim was fabricated to make the case for war. At first the government claimed that Gilligan had spoken to a low ranking intelligence officer but then released Kelly's name to the press. In a parliamentary questioning session Kelly denied making the statement and, about 6 months after telling friends "
I'll probably be found dead in the woods", was found dead in local woods. The 45 minute claim was a key part in convincing parliament and the public of the need for war but it was recently dropped by the security services. It was then that the public found that the claim originated from an Iraqi dissident living in South London. Why would a security service with the resources of a major world power rely on information from such a person we wonder? Well it all worked out nicely for the dissident, who's now the interim leader of Iraq.
http://www.FAIR.org is another good place to uncover the truth.