Campaigners have renewed demands for the London School of Economics to strip Saif al-Islam Gaddafi of his PhD, in the wake of his arrest in Libya.

Conservative MP Robert Halfon, who has campaigned for universities to reveal their links to the former Libyan regime, said it was now "vital the LSE comes clean about the relationship with Gaddafi."

He added: "Those LSE members who fêted Saif Gaddafi as a hero should be held responsible for their actions. We must never again appease dictators."

Anti-extremism group Student Rights has criticised the delay by the University of London, currently investigating allegations that Colonel Gaddafi's son plagiarised his 2008 PhD thesis. The university has promised to respond by the end of term.

The Gaddafi pledged £1.5 million to LSE's Global Governance Centre, a year after Mr Gaddafi was awarded a doctorate from the Centre. Sir Howard Davis resigned as director of the LSE over the university's links with Col Gaddafi.

Student Rights director Raheem Kassam said the reputation of the university could be "irreparably damaged".

He said: "The fact that the LSE has yet to strip Saif Gaddafi of his PhD, when he is being investigated for crimes against humanity, is unconscionable.

"Amidst accusations of plagiarism, the implication of academic corruption and the evidence of his recent brutality, the LSE must act now or admit that they are guilty of a horrific abdication of moral responsibility."

Two investigations were launched earlier this year into Mr Gaddafi and the university's connection with the Libyan regime.

The University of London panel is considering the plagiarism allegations against Mr Gaddafi; and former Lord Chief Justice Lord Woolf has led an independent inquiry into LSE's links with Libya. LSE has not yet published Lord Woolf's findings.