Proposed changes to the MoT system have been deemed as reckless by motoring groups, safety charities and insurance companies.
25 organisations, including the AA, Brake, Halfords, the RAC and Kwik Fit have urged transport secretary Justine Greening and MPs to oppose moves to change the frequency and starting point of the test.
Currently, cars must take the MoT test at three years old, then once a year thereafter, but ministers are considering plans to shift the first test to four years and then to intervals of two years.
Edmund King, AA president, said: 'The AA and three-fifths of our members believe it is a false saving, which could lead to more expensive repairs later, and that's before the safety argument.'
The reduction in frequency of tests could increase road deaths by more than 250 a year, according to Promote, an agency established in response to the Governments plan to consider reducing the frequency of MoT tests.
Nigel Bartram, senior motor underwriting manager at Aviva, said: 'The MoT is the only time some vehicles receive any safety checks and maintenance, and to reduce the frequency of this check could cost lives.'
Road safety minister Mike Penning said that despite the opposition, the consultation will go ahead regardless.
'Vehicle technology has come a long way since the 1960s when our MoT regime was introduced, which is why we want to look again at the MoT to check whether we still have the right balance of testing for modern vehicles,' he said.
'This will be a genuine consultation and we want to work with the industry and motorists to get the decision absolutely right.'