Transport Secretary Patrick McLoughlin will face questions from MPs over the Volkswagen scandal following fresh claims that Whitehall officials knew about discrepancies between test results and real-world emissions.
Louise Ellman, who chairs the Transport Select Committee, said the Government's response to the scandal had been "totally inadequate" and demanded to know who knew what and when.
Her comments follow a Channel 4 News report that officials at the Department for Environment, Food and Rural Affairs had data on emissions produced by VW vehicles and those of other carmakers in 2013 but did not act and did not publish it.
Labour MP Ms Ellman said: "It is scandalous and as this scandal unfolds there are more and more shocking revelations.
"We need to know the truth of what happened, when the department knew what was wrong and why nothing has been done about it.
"Indeed we need to see more leadership from the Department for Transport, from the minister, about what is to be done now."
She added: "As soon as Parliament resumes I'm going to be calling the Secretary of State to the Transport Select Committee to answer these questions.
"There are a number of very important issues. It is about emissions, about health but it's also about safety and it's about public confidence.
"The system of testing is supposedly independent but in practice it is the manufacturers themselves who decide who is going to do the testing and that clearly is not independent and it must compromise safety and compromise public confidence."
German car-maker Volkswagen has admitted that 11 million of its diesel vehicles worldwide are fitted with defeat device software.
The UK Government has launched an investigation to re-test cars to compare their laboratory results with real-world driving emissions
But Ms Ellman criticised the Government's response to the disclosures about VW: "Ministers say that they are now going to conduct testing to see if other vehicles are involved with the same software. But I find that answer totally inadequate. We don't know what the timetable is, it is entirely unclear who is going to do the testing and on which vehicles that testing will be carried out.
"We know about the problems with Volkswagen but are other manufacturers involved? After all, we have already been told that 11 million pieces of that software, designed to deceive, have been put into vehicles worldwide? How many of those are on UK roads?"
Channel 4 reported that in 2013 the Government commissioned a report into the levels of pollutants emitted by cars on the road, but the findings were not published in full.
Data released in response to a Freedom of Information request showed Volkswagen vehicles had higher emissions than other makes, Channel 4 said.
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