The 68-year-old former first lady was diagnosed with lymphoma (throat) cancer in August 2017.
"Yes, the death of Begum Kulsoom Nawaz is confirmed", Maryam Aurangzeb, a spokesperson of Pakistan Muslim League-Nawaz (PML-N) told AFP.
She took out rallies in support for her husband Nawaz Sharif and campaigned for his release when he was put in jail after a coup by General (Retd) Pervez Musharraf in 1999.
Sharif was ousted from the premiership a month before his wife's diagnosis.
Kulsoom Sharif was briefly a member of parliament after she won her husband's former seat in a by-election after the Supreme Court disqualified him.More news: EA under investigation by Belgian Gaming Commission
Sharif had been banned from running, but maintained his control over his eponymous party, and his return was seen as a failed gamble to save his political legacy. She served in the capacity till 2002.
Kulsoom Sharif, the wife of Nawaz Sharif, died today in London after a long battle with cancer. The couple have four children.
Iqbal had said that they had sought three names from Peoples Party but the PPP named Ahsan because they knew it would not be accepted by the PML-N.
But she was not sworn in as she was already overseas for cancer treatment. A statement by Prime Minister Imran Khan said that all facilities will be provided to the family and heirs of Kulsoom as per law.
The newly elected Pakistani government of Imran Khan has made a decision to extend all help in bringing the mortal remains of Begum Kulsoom from London. "My condolences and prayers go to the Sharif family". "May God rest her in peace", Shehbaz Sharif, the former prime minister's brother, said on Twitter. "They had to leave her behind, I don't know what they'll be going through right now".
Up until her husband's ouster past year, Kulsoom Sharif had never been a politician, but she memorably led protests after the 1999 military coup that ended a previous Sharif administration.