Volkswagen Group UK says there is “some risk” that the target to complete modifications to its vehicles fitted with emission defeat devices could be missed.

Paul Willis, its managing director, was quizzed by MPs on the House of Commons Transport Select Committee about the plan to alter 1.2 million Volkswagens, Audis, Skodas, Seats and Volkwagen vans currently in the UK’s vehicle parc.

In all, 60 models across its five brands fitted with three different engines and two different transmissions have been implicated in the scandal.

VW Group UK has said its dealer networks will begin modifications from January and has a target to complete them before the end of 2016.

Willis told MPs the carmaker was currently working with the German authorities to establish a fix which was “durable” and one which would not affect fuel consumption. “There cannot be any change in miles per gallon,” he said.

The vast majority – around 700,000 2-litre and 1.2-litre models – will only require a software patch to rectify the problem.

However, Willis told MPs that more than 400,000 cars in the UK fitted with the defeat device will require fuel injectors to be replaced as well as a software fix.

He confirmed that a voluntary recall will begin in January, with 2-litre vehicles being dealt with in the first quarter, and it is expected to be completed by the end of 2016.

He said: “I apologise to our customers for it taking so long. It’s better to be thorough and get it absolutely right.”

Owners who are inconvenienced by being without their car during the recall process would receive a loan car.

Network able to cope

However, he acknowledged that the timescale was dependent on the network being able to cope with the repairs that would need to be carried out. “There is some risk involved in that, but the goal is to get vehicles fixed by the end of 2016,” he said.

Willis revealed that VW Group UK stopped selling affected models on September 30, eight days after it had emerged that Europe was affected by the emissions scandal.

During this period another 1,000 cars fitted with defeat devices were sold.

"I couldn't stop selling cars if I didn't know which cars were affected," he told MPs. "There were eight days between when we first knew it affected Europe until I stopped selling cars and the reason for that is the complexity of the number of cars involved.”

Willis apologised “sincerely and unreservedly” for letting down customers.

"Volkswagen has significantly let down its customers and the wider public... we recognise we've fallen short of the standards expected and we will take all the necessary steps to regain trust."

"We mishandled the situation. That's why we need to fix the cars, that's why we need to get the customers in and need to put the cars right.

"We mishandled the situation without a shadow of a doubt."

Mike Hawes, Society of Motor Manufacturers and Traders (SMMT) chief executive, was also questioned at the committee meeting.

He was asked if he knew of manufacturers using methods during emissions test procedures to improve results. Examples given included taping up radiators and removing spare tyres and windscreen wipers.

Hawes said: "In my 20 years in the motor industry I have never seen or heard of any like that. These tests are independently verified by the Vehicle Certification Agency (VCA) and they would intervene if any vehicle was not in production conformity."

Dealer support

Willis confirmed that VW has changed the bonus thresholds on customer satisfaction for UK dealers so they will earn bonus "automatically". There will also be no stocking costs for the cars affected.

He said: “The second step is in the coming days, my team are meeting with all the retailers to see what we need to do next. We couldn’t exist without our retailers, they are the backbone of our business and it’s really important that we look after and support them.

“They are at the forefront of the pressure and questions from customers so it’s absolutely imperative that we work and help them.”

Volkswagen has already launched an advertising campaign in the UK apologising for breaking the trust of its customers.

The campaign ran in the UK’s national papers over the weekend.

The full advert read: “We have broken the most important part in our vehicles: your trust. Now, our number one priority is winning back that trust.

“We know that actions speak louder than words. So we will directly contact every customer affected and resolve the issue for them.

“If you have a 1.2, 1.6 or 2.0 litre diesel Volkswagen or Volkswagen commercial vehicle, it may need attention.

“If you have an EU6 diesel engine, V6 TDI or V8 TDI, or any petrol engine, you are not affected.

“To find out if your vehicle is affected visit: volkswagen.co.uk volkswagen-vans.co.uk

“In the meantime please rest assured that all our vehicles are safe and roadworthy and that we’ll continue to do everything we can to win back your trust.”

The full Transport Comittee meeting video is available here.