The UK boss of Volkswagen will be hauled before MPs today to answer questions about the diesel emissions scandal.
The German carmaker has admitted that 11 million of its vehicles worldwide are fitted with software which was used to cheat environmental tests in the US.
Close to 1.2 million vehicles are affected in the UK.
Paul Willis, managing director of Volkswagen Group UK, will appear before the transport select committee.
Transport Secretary Patrick McLoughlin and the Society of Motor Manufacturers and Traders chief executive Mike Hawes will also give evidence.
The emissions scandal was sparked by US environmental regulators who found that VW had installed defeat device software which switched engines to a cleaner mode when they underwent official testing.
Once on the road the cars produced nitrogen oxide pollutants at up to 40 times the legal standard.
A recall is expected to start in the new year with the aim of having all affected cars fixed by the end of 2016.
The committee is due to ask Mr McLoughlin what steps the Government is taking to "restore public confidence" in vehicle testing.
Steve Gooding, director of motoring research charity the RAC Foundation, told the Press Association: "Weeks after the emissions scandal broke in the US, hundreds of thousands of people who own VW Group cars here are little the wiser as to the impact on them.
"Many basic questions remain. Were the EU tests rigged by VW? What does the UK recall involve? What will happen to drivers who decide to ignore it?
"This hearing brings together the main players and we hope the committee will get some straight answers."
Andrew Pendleton, head of campaigns at Friends Of The Earth, said: "The committee must carefully and painstakingly grill VW's UK chief and Patrick McLoughlin as they have many questions to answer about this major threat to public health.
"How much did they know, not only about the company's strategy to cheat the system, but of the systematic failure of a testing regime that has allowed millions of vehicles that don't meet agreed standards onto the roads?
"Not only have motorists been deceived, but some of the 52,000 people who die prematurely in the UK each year due to air pollution will have died because of this scandal."
Mr Willis will also give evidence to parliament's environmental audit committee on Thursday.
The chair of the committee, Huw Irranca-Davies MP, said: "Toxic air pollution from traffic is contributing to thousands of deaths in the UK every year, so the cheating of car emissions tests is of grave concern.
"Questions remain about the impact of VW's actions on the UK's air quality and the Government's policy on cleaner transport."