The cause of the Irish artist's death was revealed after her first husband John Reynolds registered her death certificate last week, as first reported by the Irish Independent on Sunday.

It comes a year after the 56-year-old was found unresponsive at her home in southeast London.

The death certificate stated the singer and activist died from "exacerbation of chronic obstructive pulmonary disease and bronchial asthma together with low grade lower respiratory tract infection".

The death was certified by Julian Morris, senior coroner for Inner South London, after a coroner confirmed in January O'Connor had died of natural causes and that her death would not be investigated further.

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Two weeks before she died O'Connor told her fans that she had recently moved back to London after a 23-year absence - and she was "very happy to be home".

She said she was finishing an album that was going to be released early next year - and planned to launch a world tour spanning Australia, New Zealand, Europe and the US.

O'Connor was best known for her 1990 song Nothing Compares 2 U, the Prince cover that made her a global star - partly due to its iconic video.

She was also known for her outspoken views on subjects such as religion, war and feminism, and infamously tore up a photo of Pope John Paul II on Saturday Night Live in 1992 to protest against abuse in the Catholic Church.

In 2018, she announced she had converted to Islam and changed her name to Shuhada' Sadaqat, but continued to perform and record as Sinead O'Connor.