POLICE have confirmed that further tests have been ordered to establish the cause of death of former Liberal Democrat leader Charles Kennedy, who died on Monday at the age of 55.

A post-mortem examination has already taken place, but it is understood the results proved inconclusive.

A Police Scotland spokeswoman said yesterday: "We can confirm that further tests are being carried out to establish the cause of death. It remains a sudden and non-suspicious death and the procurator-fiscal will be sent a report.”

Kennedy led the LibDems for six years and took the party to its best election result in 2005. He resigned eight months later after revealing that he had been having treatment for a drink problem.

Speaker John Bercow set aside time in the Parliamentary schedule on Wednesday to allow members to deliver short speeches in his memory.

Prime Minister David Cameron led the tributes, saying Kennedy was “an extraordinary talent” and “a man of great principle”. He added: “At his best he was the best that politics can be, and that is how we should remember him”.

Kennedy’s ex-wife Sarah and 10-year-old son Donald watched proceedings from one of the public galleries.

Labour’s Tom Watson, who directed his speech to Donald, said: “Your father was a very great man, he stood up for what he believed in, he led a party of the centre-left with dignity and compassion and when you are older you will know your mum and dad believed in a cause greater than themselves, and you will be proud.”