London mayor Ken Livingstone has said members of the public will die if the government's controversial plans to involve private sector companies in the running of the London Underground go ahead.

He told BBC Radio 4's Today programme: "The proposal I've got in front of me now, I have not the slightest doubt, if it goes ahead, Londoners will die."

Livingstone has also confirmed he will launch legal action to prevent ministers going ahead with their plans. The mayor added that resorting to the courts was necessary because the government's proposals would not meet requirements to provide a safe, efficient and economic transport system.

A month ago hopes had been raised that a deal had been struck between Livingstone, transport commissioner Bob Kiley and deputy prime minister John Prescott.

"What has emerged as government policy is dramatically different from the signed deal we got in writing just a month ago from John Prescott which was a working way forward," claimed Livingstone.

Pressure is increasing on the government to reach a compromise. The board of Transport for London has already given approval for Kiley to launch legal action and London Assembly members have reaffirmed their opposition to the break-up of the Tube. The RMT union has announced a ballot of members on renewed strike action in protest.

Under the governments public-private partnership plans responsibility for signalling, tracks and tunnels would be divided between three private sector companies. Critics have insisted a "unified management" is necessary to prevent fragmentation.