Hugh McCartney, 23, was found dead in his flat on a rundown estate in the east end of Glasgow at the beginning of last week.

The funeral service was led by Mr McCartney and was attended by around 70 mourners including Hugh's mother Jean Murray, the politician's former wife.

The congregation heard that Hugh had written a letter to his family to be read in the event of his death.

Around 70 mourners attended the funeral

It read: "Don't feel guilty, just feel happy I am not putting myself through any more punishment."

It added: "... one message, if any of you are feeling down, stick your courage to the sticky place and get on with it."

The short letter was signed Shug - a nickname given to him by friends.

Hugh had battled drug addiction since his teenage years and he had recently been released from prison and was trying to break his habit.

During the funeral, Mr McCartney made reference to the battles Hugh had fought in his short life. He said his son had had problems but was never seen by his family as a problem.

He told the congregation: "I stand here today, not as a public figure, MP, Privy Councillor or Government Minister.

"None of these titles or honours are a help or a defence against having to deal with what is the nightmare that every parent dreads.

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"The death of your child is the most traumatic, most difficult situation that any parent will ever have to face.

Mr McCartney said that he was in the church as "Hugh's wee dad".

The Labour politician said his son was "an engaging child" who made friends easily. But he also described Hugh as a "complex young man".

"As you can tell, from the music and the words of today's service, Hugh had hopes and ambitions for himself and others," said Mr McCartney.

He went on: "Hugh loved his family deeply. Hugh was never seen by us as a problem, he was a young man with a problem. But he was our young man and will always remain our young man."

Mr McCartney said his son had never wanted to give up on life.

'Free spirit'

"He thought he could ride a tiger. He thought he could be a free spirit - and he was. But it was the tiger that captured Hugh - not Hugh the tiger.

"But in all of these traumas and turmoil he held onto something so important to his very last breath and that was the love he had for his mum, his dad, his sisters and his family," said Mr McCartney.

After finishing his address, Mr McCartney patted his son's coffin before sitting down.

The congregation at Calton Parkhead Church heard songs and hymns that Hugh himself had chosen for his own funeral when he realised his drug addiction was threatening his life.

Mr McCartney and his former wife were accompanied by their daughters, Yvonne and Karen.