* BBC film crew posed as students and staff to film in secret
* University says its students were put at "grave risk"
* Test for new BBC boss, hired to rebuild after sex scandal
LONDON, April 15 (Reuters) - The new head of Britain's BBC stumbled into a new threat to its journalistic reputation on Monday after its decision to use university students as a cover to film secretly in North Korea was branded "reckless and irresponsible".
Less than two weeks after taking up his post at an institution in turmoil after a sexual abuse scandal, BBC Director General Tony Hall faced accusations that his flagship news programme had used British students as "human shields".
Hall was brought in to rebuild the BBC's image after accusations of a cover-up, managerial failings and editorial mistakes over abuses by Jimmy Savile, one of its best known entertainers.
One BBC news executive said discussions about the documentary had gone "right to the top" and that Hall had been involved in talks about the film in recent days.
It raised questions about its legal, ethical and moral position at a time when its managers are under unprecedented scrutiny.
British universities said the BBC, with the North Korea documentary, had endangered students and damaged their ability to work in sensitive areas around the world.
"The entire enterprise was reckless and irresponsible from start to finish, as well as deeply dishonest," said London School of Economics (LSE) Director Craig Calhoun.
He said the documentary had put LSE students at "grave risk" in the hermit east Asian state, which has threatened the United States and South Korea with nuclear attacks.
Nicola Dandridge, who leads the body that represents nearly all Britain's universities, said the BBC "might not only have put students' safety at risk, but may also have damaged our universities' reputations overseas".
Calhoun said BBC journalists posed as LSE staff or students to "trick their way past" restrictions on Western journalists working in North Korea.
Producers had told students only that they would be accompanied by "a journalist", not a three-strong crew from Panorama, one of its best-known current affairs shows, he added.
The BBC rejected LSE calls to cancel the programme, due to be aired in Britain on Monday evening, and reaffirmed that it was in the public interest.
Ceri Thomas, BBC News' head of programmes, said it had explained the dangers of travelling with the TV crew to the students and that it had been worth the risk.
"If we had any suggestion that lives were at risk or anything approaching that - either the BBC team's lives or the lives of the students - then we wouldn't have gone anywhere near this," Thomas told BBC radio.
Media commentators were divided over the BBC's tactics.
Former BBC producer Charlie Beckett, who founded a journalism think-tank at the LSE, said the filming was "unnecessarily reckless".
However, John Lloyd, director of journalism at the Reuters Institute for the Study of Journalism, said the timing and content of the film made it "extremely valuable". (Additional reporting by Sarah Young and Kate Holton; Editing by Mark Heinrich)