"I have received information this evening that Ken is alive," said Paul Bigley on Sunday.
He was speaking by telephone from the Netherlands to Labour MPs at the annual conference of Prime Minister Tony Blair's party, at the invitation of a group of party members opposed to the Iraq war.
Bigley is reportedly being held by al-Tawhid and al-Jihad, a group alleged to be sympathetic to Jordanian-born fugitive Abu Musab al-Zarqawi.
Paul Bigley criticised Blair for his handling of the issue.
"Help me keep him alive," he pleaded with a group of MPs.
"Mr Blair's silence for the past 10 days is a kiss of death to my brother," he said.
"Mr Blair, you're doing it the wrong way."
Yasir al-Sirri, director of London's Islamic Observatory, told Aljazeera he had also been told Bigley is still alive.
"The man is alive. We sent a message to al-Tawhid and al-Jihad last Thursday, and they got a message from Tajdeed al-Islami (Islamic Renovation) yesterday," he said.
"We got [a] positive response from them through a middleman who said they will take into account the pleas [for releasing Bigley] from the Islamic Monitor and Islamic Renovation."