* Former Murdoch editor Coulson denies hacking charges
* His lawyer says prosecution case has been cavalier
* Coulson worked as PM Cameron's media chief
LONDON, May 28 (Reuters) - The prosecution of Andy Coulson, British Prime Minister David Cameron's former media chief, over phone-hacking at Rupert Murdoch's News of the World tabloid has been cavalier and unfair, his lawyer told a London court on Wednesday.
The jury at London's Old Bailey court, where Coulson and six others are on trial, must not think a senior figure at Murdoch's company had to be held to blame for the scandal which engulfed the media mogul's empire in July 2011, said Coulson's lawyer Timothy Langdale.
Coulson, who edited the News of the World before moving on to work for Cameron's Conservative Party, denies charges of conspiracy to intercept voicemails on mobile phones and authorising illegal payments to public officials.
He quit the Murdoch tabloid in 2007 after Clive Goodman, its former royal editor, was jailed for hacking phones of royal aides, saying he was ignorant of what had happened but took ultimate responsibility.
News International, the British newspaper arm of News Corp. , said Goodman was a rogue reporter but further evidence emerged in 2011 that the practice was more widespread with victims including a murdered schoolgirl, leading to a furore which prompted Murdoch to shut the 168-year-old paper.
Police also relaunched an inquiry which led to Coulson's arrest and three former journalists admitting hacking offences.
In his closing speech to the trial, which began exactly seven months ago, Coulson's lawyer said the case which had attracted huge public interest and scrutiny should be "fair, open-minded but rigorous".
"We suggest as far as Mr Coulson is concerned it has been none of those," Langdale said. "It's almost as if the juggernaut of the police investigation and this prosecution must keep moving whatever legitimate obstacles are thrown in its path.
"There must be no thought ... that somebody high up in the organisation has to pay for phone-hacking, no thought that after a trial of this length and magnitude there must be a conviction of someone."
Goodman and Dan Evans, another of the paper's former reporters who has admitted hacking, have told the trial that there was hacking on an industrial scale under Coulson's editorship and he was fully complicit.
Langdale said there was no evidence for such claims or any suggestion Coulson knew about hacking, describing Evans and Goodman, who was sitting next to Coulson in the dock, as thoroughly unreliable.
"Both have been demonstrated to be liars," he told the jury.
"A notable factor of this case is the prosecution has failed to call before you a single witness to testify that Andy Coulson was involved in phone-hacking at the News of the World who does not have an agenda of their own."
He said an email, held up by the prosecution as a hacking instruction, in which Coulson told a senior employee to "do his phone" was a misconception and there was no evidence to suggest any phone interception followed.
"Why are there no emails requesting hacking or sanctioning hacking or anything of the kind?" Langdale said. "The prosecution approach we suggest has too often been broad-brush not to say cavalier."
Coulson, Rebekah Brooks, the former chief executive of News International, and the paper's ex-managing editor all deny phone-hacking offences.
Coulson, Brooks and Goodman have pleaded not guilty to charges relating to illegal payments, and Brooks and three others deny trying to hinder the police investigation. The trial continues. (Editing by Kate Holton)