Backbench Labour MPs have pleaded with the Deputy Prime Minister John Prescott not to proceed with the part privatisation of the air traffic system.

Speaking during a Commons debate on the government's transport bill, Labour MP Gwyneth Dunwoody, the chair of the Commons Transport Select Committee, urged Mr Prescott to think again.

She told MPs that safety standards would be undermined if the government went ahead with its plans to sell off 51% of National Air Traffic Services.

Ms Dunwoody was joined in her protest by former Labour transport minister Gavin Strang who said bringing the profit motive into Nats would jeopardise the safety record of the best air traffic system in the world.

Mr Strang said the proposed public-private partnership could undermine national security in instances where intelligence on terrorist operations would make it essential for the government to take swift control of the whole of Nats.

Mr Strang told MPs: "The Tories never got around to this privatisation - I think the decisive case against it is the national security issue."

He warned ministers against pursuing the proposals, saying: "I know that I am speaking for more than 50 Labour MPs when I make this case and I hope the government is going to listen."

Moving the amendment to the bill opposing the plan, Liberal Democrat MP Michael Moore said: "The facts stand for themselves - the public record is first class and the ethos of the personal is beyond reproach.

"So the question many ordinary people will ask is why tamper with this highly successful set up."

Safety concerns rejected

But Mr Prescott told the House: "The concern that the profit motive will undermine safety has not been proven."

He said that the Civil Aviation Authority would continue to oversee safety and that the proposed part privatisation would enable the Nats to invest and to cope with the projected growth in air traffic.

Joining the debate former Tory minister Michael Portillo called on potential rebels to vote with the Conservatives and scupper the planned PPP when it reaches its committee stage.

He told Labour MPs: "This government falls over when you blow hard enough and all they have to do is come with us and vote with us."

Congestion charging

The deputy prime minister also unveiled plans to enable local authorities to bring in congestion charging on cars.

The money raised he said would be ring-fenced for at least 10 years, enabling local authorities to invest the money raised in improving transport locally.

The hypothecation of taxes was, Mr Prescott said, "a truly radical proposal that no British government has ever done before".

Mr Prescott also unveiled proposals for a Strategic Rail Authority to bring, "public accountability back to the rail industry".

The Conservative transport spokesman John Redwood then launched a stinging attack on Mr Prescott's bill.

Prescott's 'cowardice'

Baiting Mr Prescott on the recent handover of day to day responsibility for transport to Transport Minister Lord Macdonald, Mr Redwood dismissed the deputy prime minister's proposals as a "non-bill from a non-minister".

He said the sale of Nats was being undervalued by the government.

Mr Redwood attacked Labour saying the government's policies would "bash the motorist" and tax people off the road.

Turning to local authorities gaining the right to bring in parking and congestion charging he said Mr Prescott's "cowardice is such that he would rather see someone else take the immediate flak for imposing the charges."

An amendment warning that private profit could "jeopardise safety standards", was later defeated by 321 votes to 33. Although 50 Labour MPs originally signed up to the amendment, none of them backed it although some did choose to abstain.

The bill gained its second reading by 358 votes to 163.