Update - 1.2 million UK cars affected (29 September)

Volkswagen has confirmed nearly 1.2 million UK cars and vans using the EA 189 engine will have the software behind the scandal. These include Volkswagen, Seat, Audi and Skoda cars, and some vans.

Over half a million of these are Volkswagen cars with models such as the Golf and Passat among others affected.

Volkswagen says it will announce plans for how it will solve the problem in the next few days. It will then send vehicle identification numbers to retailers so that customers can check if their vehicle is affected.

Finally, Volkswagen will then contact owners with the next steps - although at the moment these are unknown.

Here's everything you need to know about the scandal so far.

What has Volkswagen been accused of doing?

All cars are tested for the amount of harmful emissions they produce and given an emissions rating. Volkswagen admitted to installing software to its cars that could tell when the car was being tested on the US and cheat to give lower readings. The exact nature of the software is unknown at this time.

This means that real world emissions could be much higher than when the cars were tested. Reports suggest cars with a particular Volkswagen diesel engine - the EA 189 engine - could emit up to 40 times the amount of nitrous oxide readings showed in tests.

In total, nearly half a million cars in the US could have been affected.

So it's just the Volkswagen cars in the US that are affected?

Unfortunately, no. Volkswagen says 11 million cars in total could be affected, including Volkswagen cars such as the Golf, Beetle and Passat, and other Volkswagen-owned brands such as Audi that use the same engine.

However, there is no evidence the software was used on cars tested under European tests, which are different from those in the US. Even if the software was present on UK cars, it does not necessarily mean it was used to cheat European tests in the same way it did in the US.

The Society of Motoring Manufacturers and Traders (SMMT) says: “Consumers should be reassured that cars sold in the UK must comply with strict European laws. All cars must complete a standard emissions test, which, unlike in the US, is independently witnessed by a government-appointed independent agency.

“On the separate on-going debate about real world testing, industry accepts that the current test method for cars is out of date and is seeking agreement from the European Commission for a new emissions test that embraces new testing technologies and which is more representative of on-road conditions.”

Is my Volkswagen car dangerous?

No need to panic, the cars are still safe. Here is what Volkswagen has to say:

"All affected vehicles are absolutely safe and roadworthy. The matter at hand applies exclusively to emitted pollutants. We will resolve this. It goes without saying that we will take full responsibility and cover costs for the necessary arrangements and measures.

"The software in question does not affect handling, consumption or emissions. A noticeable deviation between bench test results and actual road use was established solely for Type EA 189 engines. Volkswagen is working hard to eliminate these deviations through technical measures."

What Volkswagen cars are affected?

Once again, we do not know at this point. Volkswagen says it cannot specify which models are affected but it is working to find out.

Volkswagen says: "Please understand that we are currently not able to specify which models and years of construction are affected. We will provide you with further information as soon as possible.

"Volkswagen will do everything to fully regain the trust so many people put in us."

I have a Volkswagen car. What do I do now?

Firstly, you will have to wait to see if Volkswagen cars are affected in the UK. If they are - and there is no suggestion they are - Volkswagen could announce a recall to fix the problem. This will mean you will have to return your car to be fixed - free of charge.

This sounds like bad news for Volkswagen...

It is. chief executive Marton Winterkorn has resigned from his position and Volkswagen shares plummeted when the news broke, amid fears it could face billions of dollars of fines and repayments. The scandal will also reflect badly on Volkswagen and damage much of the trust it has created in its cars. It will also damage trust in diesel engines as a whole, after their eco-friendly credentials have been put under the spotlight.

What about other cars?

There is no doubt other cars and car makers will be looked at in the US, but there is no evidence this practise was more widespread than the single engine on Volkswagen diesel cars at this point.