Please note that the legal position in relation to public officials and the law of defamation in various countries were summarised in the judgment of the House of Lord in Reynolds v Times Newspapers (28 October, 1999).
In the United States the leading authority is the well-known case of New York Times Co. v. Sullivan 376 U.S. 254. Founding itself on the first and fourteenth amendments to the United States Constitution, the Supreme Court held that a public official cannot recover damages for a defamatory falsehood relating to his official conduct unless he proves, with convincing clarity, that the statement was made with knowledge of its falsity or with reckless disregard of whether it was false or not. This principle has since been applied to public figures generally.
In India the Supreme Court, in Rajagopal v. State of Tamil Nadu (1994) 6 S.C.C. 632, 650, held that a public official has no remedy in damages for defamation in matters relating to his official duties unless he proves the publication was made with reckless disregard of the truth or out of personal animosity. Where malice is alleged it is sufficient for the defendant to prove he acted after a reasonable verification of the facts.
In Australia the leading case is Lange v. Australian Broadcasting Corporation (1997) 189 C.L.R. 520. The High Court held unanimously that qualified privilege exists for the dissemination of information, opinions and arguments concerning government and political matters affecting the people of Australia, subject to the publisher proving reasonableness of conduct. The High Court regarded its decision as an extension of the categories of qualified privilege, and considered that the reasonableness requirement was appropriate having regard to the greater damage done by mass dissemination compared with the limited publication normally involved on occasions of common law qualified privilege. As a general rule a defendant's conduct in publishing material giving rise to a defamatory imputation would not be reasonable unless the defendant had reasonable grounds for believing the imputation was true, took proper steps, so far as they were reasonably open, to verify the accuracy of the material and did not believe the imputation to be untrue. Further, the defendant's conduct would not be reasonable unless the defendant sought a response from the person defamed and published the response, except where this was not practicable or was unnecessary.
In South Africa the issue has not been considered by the Constitutional Court. In National Media Ltd. v. Bogoshi 1998 (4) S.A. 1196, 1212 the Supreme Court of Appeal broadly followed the approach of the Court of Appeal in the Reynolds v. Times case and the Australian High Court in the Lange case. Press publication of defamatory statements of fact will not be regarded as unlawful if, upon consideration of all the circumstances, it is found to have been reasonable to publish the particular facts in the particular way and at the particular time. In considering the reasonableness of the publication account must be taken of the nature, extent and tone of the allegations. Greater latitude is usually to be allowed in respect of political discussion.
In New Zealand the leading case is the Court of Appeal decision in Lange v. Atkinson  3 N.Z.L.R. 424. The Court of Appeal held that members of the public have a proper interest in respect of statements made about the actions and qualities of those currently or formerly elected to Parliament and those seeking election. General publication of such statements may therefore attract a defence of qualified privilege. The exercise of reasonable care by the defendant is not a requirement of this defence. This decision is currently under appeal to the Privy Council.