The threat of terrorist attacks on Britain's transport system "remains grave" and should be countered by every means possible, MPs warn today.
In a new report, the Commons transport committee acknowledges that the security costs to industry are high, but insists "there can be no compromise on this point".
The committee began an investigation into the security of Britain's roads, trains and airports in the wake of the July 7th bombings in London, and today publishes its preliminary findings.
Evidence given by transport secretary Alistair Darling and Transec, the department responsible for ensuring transport security, were "broadly reassuring", it says.
And the committee "warmly welcomes" a pilot scheme to introduce airport-style scanners in Paddington station from early January, as a way of increasing security.
But it notes a number of complaints from within the transport sector at the cost of such measures, warning that cooperation between government and industry was crucial.
"We hope that no city will experience events similar to those which took place in London on July 7th 2005. These events demonstrated the paralyzing disruption terrorist attacks can cause to the transport infrastructure of a major city," the report says.
"The threat of further attacks remains very high. The means at the disposal of the UK government must be deployed effectively and efficiently."
A key concern arises from the "disquieting evidence" presented by the industry, including allegations of faulty train radios in use on the London Underground.
These, MPs were told, could compromise the ability to respond to an attack, while there were also complaints about the alleged inadequacies in the identification of suspect packages.
In addition, the report notes that the government is lacking in its assessment of how much new security measures would cost. For example, there had been no regulatory impact assessment on their impact on the airline industry, a fact MPs find "surprising".
"We are not in a position at present to conclude whether the complaints we heard from the transport industry about the current protective security arrangements, or to gauge their overall significance," it says.
However, the report warns that it is "essential" that the appropriate security measures be implemented, maintained and updated wherever necessary.
Today's report also looks at the importance of public vigilance in tackling the threat of terrorism on the transport system, and urges the government and Transec to make more of an effort to enlist people's support.
With regards to media reporting of security measures, the committee disputes Transec's claim that highlighting weaknesses was not helpful, and could tempt "those with questionable motives" to exploit them.
Describing this as a "simplistic" response, the committee warns: "We expect the relevant authorities to deal swiftly and effectively with security weaknesses, and with those who would exploit them."