Brooks faces fights on all fronts back at Murdoch's London HQ

(Repeats Sunday's story with no change to text)

* Rebekah Brooks returns as News UK chief executive

* Cleared in 2014 of involvement in phone hacking scandal

* Faces battle to revive readership, rebuild contacts

By Kate Holton and Mark Hosenball

LONDON/WASHINGTON, Sept 6 (Reuters) - When the once toxic Rebekah Brooks returns to run Rupert Murdoch's British newspapers on Monday she will face the toughest challenge of her career -- rebuilding her reputation and the company in the harsh glare of the public spotlight.

Brooks, the media mogul's protegee who was cleared last year of being part of a criminal phone hacking campaign to dig up news stories, will resume oversight of Britain's The Sun and The Times papers as News UK chief executive, following a four-year battle to clear her name.

On her return, she will face a new fight to stem falling circulation at The Sun, the move of advertisers online and the simmering resentment from some staff who feel Murdoch sought to protect Brooks above all others when faced with the crisis engulfing his company.

Renowned for her networking abilities, the 47-year-old will also have to find a way to rebuild ties with those who run the country after her 2011 fall from grace led to her vilification.

"The challenge now is to work out how she's going to operate this time around given her profile and given that her big modus operandi in the past was relationships and networks," said one former senior executive from Murdoch's British newspaper arm.

"The fact is that politicians and business figures still need to have a strong relationship with News UK."

Brooks' return marks a spectacular comeback for someone who worked her way up from the lowest rung on the newsroom ladder to become one of the most powerful women in Britain and a close friend to the last three prime ministers.

That all seemed set to end in 2011 when the News (Other OTC: NWSAL - news) of the World tabloid she once edited admitted its journalists had hacked into thousands of voicemails including those of a murdered schoolgirl to break news, sparking widespread public revulsion.

DEEPLY AFFECTED

So tarnished was Brooks that Prime Minister David Cameron, once a close friend, distanced himself, while lawmakers who once eagerly sought Murdoch's approval turned their back.

Brooks was later arrested and charged with conspiring to hack into phones, bribing public officials and perverting the course of justice but was cleared following a eight-month trial.

Andy Coulson, a former colleague and lover who went on to become Cameron's spokesman, went to jail, while a handful of other journalists were also found guilty. A similar probe is still going on at rival Trinity Mirror (LSE: TNI.L - news) .

"Rebekah has gone through a personal experience which we can only guess at how deeply that has affected her, and the Rebekah we are going to see in the future is going to be different," a second former colleague said on the condition of anonymity.

A senior company insider said people who spent time with Brooks over the last couple of months during her visits to News Corp headquarters had noted that she was now a much more congenial person than before.

Despite the acquittal, critics of the company were dismayed by her return, noting Brooks' defence had been that she could not be expected to know what her staff were doing.

Chris Bryant, an opposition lawmaker, said Murdoch was "sticking two fingers" -- a British gesture of insult -- at the public, while media analysts said it signalled that his News UK operation was ready to put the crisis behind it.

The senior company insider said Brooks had been given her old job back because she had been fully vindicated in the trial.

The next challenge for Brooks will be tough, however. In her four-year absence, Britain's press, known collectively as "Fleet Street" after the London lane where the papers were based for generations, has changed significantly.

Sales of The Sun, Britain's biggest-selling newspaper, have fallen 34 percent since she left, while the paper has failed to carve out a niche online unlike fierce rival the Daily Mail which boasts one of the most popular websites in the world.

The Times has fared better, with sales down by 11 percent, while an online pay wall helped the paper to post an operating profit for the first time in 13 years in 2014.

The first major decision Brooks and Murdoch will face is on what stance their papers should take on Britain's pending referendum on membership of the European Union.

In that she will be joined by Tony Gallagher, a former editor of the right-leaning Daily Telegraph and deputy editor of the Mail who is to join as the editor of The Sun.

Prosecutors have also said they are still considering whether to bring corporate charges against Murdoch's British newspaper business, while the resentment over how the crisis was handled internally has not gone away.

"The most generous thing you could say about her is that her lack of managerial oversight and due diligence during a period which brought this fine company to its knees is something that few people will ever forget or forgive," said a third, recently departed insider, speaking on condition of anonymity. (Editing by Mark Potter)