The tape, released on Wednesday, showed Bigley squatting down in an iron cage and dressed in an orange jumpsuit of the sort worn by Muslims detained at Guantanamo Bay.
Bigley was quoted as saying: "Tony Blair is lying, lying when he says he's negotiating. My life is cheap. He doesn't care about me.
"All these people want is the female Iraqi prisoners free. They don't want to kill me. They could have killed me a week, two, three weeks ago, whatever.
"All they want is their sisters out of prison and back with their families where they belong," he added
The British engineer, who was seized in Baghdad nearly two weeks ago, was shown with a metal chain wrapped around his neck and binding his hands and feet. He appeared haggard and distraught.
A black banner bearing the name of his captors, the al-Tawhid wa al-Jihad group, was posted above the cage.
The group, which is allegedly led by the Jordanian Abu Musab al-Zarqawi, has already beheaded two Americans who were seized along with the Briton.
It has said Bigley will be next if its demands are not met, but has not set a deadline.
The three were working for a UAE-based construction firm operating on a US military base in Iraq.
Bigley last appeared in a videotape on 22 September pleading with Blair to save his life.
Bigley said Blair has not been
negotiating for his release
The fresh pressure on Blair - who insists he is doing all he can while refusing to negotiate the insurgents' demands to free Iraqi female prisoners - came as he sought to move on from Iraq and focus on domestic policy.
The images of Bigley also contrasted with the jubilation in Italy where two aid workers who were released by captors in Iraq, arrived on Tuesday.
The captive's brother Paul Bigley, who is acting as a spokesman for the family, said it was a relief to see the building engineer alive but painful to see him in such a state.
"It's absolutely appalling. There's no other word for it: Heart-wrenching. This is the age of technology doing its best," he told the BBC.
"They've had a worldwide coverage that nobody, not any publicity agent, could dream of. I hope they appreciate that fact and eventually release Ken as a reward for that publicity."
London and Washington have said they will not negotiate - and the US says it holds only two women in Iraq, both top weapons scientists from the days of Saddam Hussein.
"All these people want is the female Iraqi prisoners free.
They don't want to kill me. They could have killed me a week, two, three weeks ago, whatever"
At least two other Western captives are still held in Iraq - French journalists Christian Chesnot and Georges Malbrunot.
Some 30 foreign captives are thought to have been killed in Iraq since a wave of abductions started in April.
Paul also told Sky television the family would not show the latest video to the captive's 86-year-old mother, Lily Bigley, for fear of upsetting her.
Pressure on Blair
She recorded a video appeal to the kidnappers last week and is in hospital in Liverpool being treated for stress related to the ordeal.
Paul said the rest of the family would be "a little bit euphoric that the man is still alive".
"But they won't be particularly happy at his position and the state he's in. But the man's alive. There is a little bit of communication going on so let's continue this march."
The British premier is under
immense pressure to save Bigley
He added that Blair should resign and that would end the crisis.
"I think if he leaves office, Ken'll be home tomorrow on a plane."
In response to the latest appeal from Bigley, the British premier said the United Kingdom would respond to the captors if they made contact.
"They have made no attempt to have any contact with us at all. If they did make contact, it would be something we would immediately respond to," Blair said.
"We don't know where they are and they are not in contact with us. It's impossible for us to make contact with them," he said, adding his government was doing everything it could.
Al-Tawhid wa al-Jihad can be understood to mean the unity of God and the holy struggle.