The coroner who oversaw the inquest into the death of singer Amy Winehouse has resigned after her qualifications were questioned - raising the possibility the investigation may have to be held again.

The Back To Black singer's relatives said they were still absorbing the implications of the news and were seeking legal advice.

In October 2011, Suzanne Greenaway had ruled that the soul singer had died from accidental alcohol poisoning.

Greenaway had been appointed an assistant deputy coroner in London in 2009 by her husband, Coroner Andrew Reid.

But she resigned in November after authorities learned she had not been a registered UK lawyer for five years as required. She had practised law for a decade in her native Australia.

"I appointed my wife as an assistant deputy coroner as I believed at the time that her experience as a solicitor and barrister in Australia satisfied the requirements of the post," Mr Reid said in a statement today. "In November of last year it became apparent that I had made an error in the appointment process and I accepted her resignation."

Greenaway oversaw 12 inquests in Camden, the north London borough where Amy lived, and others in eastern London.

In a statement, Amy's family said they were "taking advice on the implications of this and will decide if any further discussion with the authorities is needed".

Her father Mitch reassured followers on Twitter, writing: "Don't worry about coroner nonsense. We are all ok. Mitch."

A security guard found the 27-year-old star dead at her home in July last year. At the October inquest, Greenaway delivered a verdict of death by misadventure, saying the singer suffered accidental alcohol poisoning when she resumed drinking after weeks of abstinence.