Millions of pounds earmarked for the congestion charge expansion should be spent on improving security, the London Assembly's Lib Dems have said.
The congestion charge scheme may be extended westwards
They also want plans to install mobile phone access on the Tube network to be reassessed because of concerns signals can be used to trigger bombs.
The ideas are part of the party's 10-point plan to make London safer.
Transport for London said no decision has been made on the extension but funds from it will go towards security.
Assembly members said a £55m investment in security could be paid for by scrapping the proposed westward extension of the congestion charge.
In June, Transport for London (TfL) announced plans to introduce mobile phone transmitters in all 270 London Underground stations within the next three years, with expansion into all tunnels from 2008.
However, the Lib Dems said signals can be used to remotely detonate bombs.
The March 2004 Madrid bombings that killed nearly 200 used mobile phones, although these were detonated by the phones' alarm functions.
TfL is pressing ahead with the plans as it said it was not aware of any attacks where the signals have been used to detonate.
Lib Dem London Assembly leader Graham Tope said: "If they are going ahead regardless without reviewing it I think that is stupidly irresponsible."
The Lib Dems suggested merging British Transport Police's London division with the Metropolitan Police to improve co-ordination.
A TfL Spokesperson said : "No decision has yet been made on whether or not the congestion charging zone will be extended.
"However, if the zone was extended further revenues would be raised to pay for an improved and more secure transport system in the capital."
He added TfL has invested in security including funding an extra 200 British Transport Police Officers, CCTV on all buses by the end of the year and an increase in CCTV provision on the Tube network.
The 10-point Lib Dem plan will be put forward at a meeting of the Metropolitan Police Authority on Thursday.