A leading British university criticised the BBC on Sunday for arranging an academic trip to North Korea to make an undercover documentary, saying it had put students who were unaware of the plans in danger.

The London School of Economics (LSE) said three BBC journalists - including the respected reporter John Sweeney - joined a student society trip at the end of March, posing as tourists to make a film about the secretive state.

The university said the students had been told "a journalist" would accompany them, but it had not been made clear the BBC's aim was to use the visit to record an undercover film for "Panorama", a current affairs programme.

"This was not an official LSE trip," Craig Calhoun, the Director of the LSE, wrote on Twitter. "Non-students & BBC organised it, used the society to recruit some students, & passed it off."

Tensions in the Korean peninsula have escalated in recent weeks, with North Korea threatening nuclear war against the United States and South Korea.

Alex Peters-Day, general secretary of the LSE's student union, told Sky News the students were only told of the BBC's intentions at a very late stage, with one saying she was only informed when they were on the plane to North Korea.

The university said Sweeney, who graduated from the LSE in 1980, had posed as a history PhD student at the university to gain entry to the country even though he currently had no connections with the institution.

"BBC staff have admitted that the group was deliberately misled to the involvement of the BBC in the visit," the LSE said in an email to staff and students released to the media.

"It is the LSE's view that the students were not given enough information to enable informed consent, yet were given enough to put them in serious danger if the subterfuge had been uncovered prior to their departure from North Korea."

"STUDENTS WARNED"

It said the LSE's chairman had asked the BBC to pull the documentary, which is due to be shown on Monday, but the broadcaster's Director-General had refused.

"The students were all explicitly warned about the potential risks of travelling to North Korea with the journalist as part of their group," a BBC spokesman said on its website.

"This included a warning about the risk of arrest and detention and that they might not be allowed to return to North Korea in the future."

Sweeney also defended his actions on Twitter. "The LSE put out a statement which we dispute," he said.

"We did go to North Korea Undercover. The North Korean agency unhappy. LSE students knew and understood what was at stake for them before trip. They consented."

Panorama's website said Sweeney had spent eight days undercover "inside the most rigidly-controlled nation on Earth".

"Travelling from the capital Pyongyang to the countryside beyond and to the De-Militarised Zone on the border with South Korea, Sweeney witnesses a landscape bleak beyond words, a people brainwashed for three generations and a regime happy to give the impression of marching towards Armageddon," it said.

The LSE said aspects of North Korea were legitimate objects of study in several academic disciplines but said the BBC may have seriously damaged the university's reputation, and jeopardised future visits to North Korea and other countries.

"BBC story put LSE students at danger but seems to have found no new information and only shown what North Korea wants tourists to see," Calhoun wrote.