The former Northern Ireland Secretary James Brokenshire has died at the age of 53.
In a statement, his family said he died surrounded by family in hospital after a battle with lung cancer.
He was hospitalised on Sunday when his condition rapidly deteriorated.
The Taoiseach Micheál Martin said he was “deeply saddened” at the news.
“A dedicated politician and public servant, whose sincerity and commitment shone through, especially in the context of his work in Norther Ireland,” he said.
“My sympathies to his wife Cathy, children and family.”
Mt Brokenshire resigned his position in January 2018 to have surgery on lesion in his lung.
At the time, the Foreign Affairs Minister Simon Coveney said his “unwavering commitment” to restoring powersharing in the North had been “hugely important.”
He said it would be “testament to the quiet, understated but hugely valuable work of James Brokenshire” if the Northern Irish institutions could be reinstated.
The British Prime Minister Boris Johnson said it was “desperately sad” to hear the news.
“James was the nicest, kindest and most unassuming of politicians but also extraordinarily effective,” he said.