The Conservative Senedd Member Mohammad Asghar has died after he was rushed to hospital.
The Welsh Ambulance Service confirmed they were called to an 'emergency' in Newport on Tuesday morning.
Mr Asghar represented the South East Wales region since 2007 when he was elected for Plaid Cymru.
In 2004, he became Wales’ first Muslim councillor, representing the Victoria Ward in Newport, before switching parties to the Conservatives in 2009.
His daughter, Natasha, paid tribute to her father following the news. She said she "cannot imagine a life" without him.
Leader of the Welsh Conservatives, Paul Davies MS, also paid tribute to his colleague, who was known as Oscar. He said he was "proud of his roots" and made his mark as the first-ever BAME Member of the Senedd.
This news is a devastating blow to the Conservative Group in the Welsh Parliament.
The Secretary of State for Wales, Simon Hart, described Mr Asghar as "an extremely significant figure in Welsh politics".
He said: “As both Wales’ first Muslim councillor and first ethnic minority member of the Senedd, Mohammad Asghar was an extremely significant figure in Welsh politics and has contributed so much to his community and the country since settling here as a young man.
“His loss is terrible news. He will be fondly remembered and I would like to pay my condolences to Mohammad’s family, friends and constituents.”
Tributes have been paid by other colleagues and current Members of the Senedd who were "shocked and saddened" by the 74-year-old's death.
Plaid Cymru MS, Rhun ap Iorwerth, said Mr Asghar represented his region with 'pride'.
He said, ''Deepest condolences to the family of Mohammad Asghar. We disagreed on much, but batted together in the debate on having a Welsh cricket team, an issue on which he spoke with real passion! Oscar represented his region with pride.''
The First Minister Mark Drakeford said his presence in the Senedd would be missed.
Flags have been lowered outside Senedd buildings as a sign of respect. Tributes are set to be paid during Plenary.
The Llywydd of the Senedd, Elin Jones MS, said: “I am so saddened by the sudden death of our dear colleague, Mohammad Asghar.
“He will be missed by all in our Senedd. He was a friend to all across parties and was a true champion of his region and his country.”
The chairman of Welsh Conservatives, Lord Byron Davies, said he was 'deeply saddened' by his colleague's passing.
''He was a very valued and active member of the Welsh Conservative family and my heartfelt condolences go to his wife Findaus and daughter Natasha,'' he added.