For years, it has been a designer's dream to produce a fully functional electric car that can do everything its petrol-engined equivalent is capable of. Significant steps have been made, but the downfalls have always been the size of the batteries needed and the inability of such vehicles to travel long distances on a single charge.

But the need for green alternatives has fuelled technological development, with companies such as Toyota leading the field in the development of hybrids. These combine petrol and electric motors, reducing fuel consumption but allowing the car to have a full capability.

The best example of this to date has been the Toyota Prius, with significant owners being both the Mayor and Bishop of Oxford.

These cars are greener, not just because they use less petrol but produce fewer emissions and as a result provide company car owners with a much lower tax bill.

Now Toyota's self-contained luxury brand, Lexus, has produced its own hybrid car, the GS 450h, which raises the bar considerably. This is a remarkable vehicle and among the most technologically advanced on the road today.

It effectively has two engines a 286bhp 3.5 litre petrol unit and a 190bhp electric motor, which work together.

The combination means this large car can hurtle to 60mph in just 5.9 seconds, apparently effortlessly. At the same time it returns more than 30mpg around town.

How does it do this? The simple version is that at speeds of 20mph or below, the car runs solely on the electric motor. The petrol engine only cuts in as you move beyond that, but the electric unit will then provide extra power for accelerating hard and overtaking.

Starting the car is an unnerving experience. There you are, ready to go. You plant your foot on the brake and push the starter button. Nothing happens.

At least it sounds like nothing has happened. But shift the car into drive and it moves off completely silently.

There literally is no sound even if you lean out of the window, you can't hear anything. After a little practise I realised the only way you know the car has started is by an audible ping' after you have depressed the starter button for a few seconds.

Although this is fantastic, pedestrians may think otherwise and in the short time I had the car, people were walking obliviously behind it just as I was about to reverse.

When you do notice the petrol engine cut in, it is virtually seamless no jerk or jolt, just a smooth delivery of power.

And there is bags of that. Put your foot down and the car is up to the legal maximum in the blink of an eye but with no fuss, just hushed refinement.

The beauty of this system is that rather than having to compromise performance with an electric motor, the Lexus uses it to enhance power providing superb speed and acceleration.

With little or no noise interference from the engine, it allows you to enjoy the finer points of what is a fully loaded' luxury vehicle.

The excellent Paul Levinson stereo incorporates not just CD and MP3 players but a DVD, although you can only use it when stationary.

Both driver and passenger have climate control systems, including air conditioning, and the seats are not just heated but can have cool air blown through them, which is a comfort on hot days when the leather can become sticky.

The car corners well and the seats themselves are very comfortable, and it is a vehicle you look forward to driving. If you spend a lot of time on the road, this is the car for you.

Cruise control is also standard but carrying on the high-tech approach, it has the ability to sense a vehicle in front and slow down accordingly.

Effectively the car can drive itself on long motorway journeys which I am not too convinced about. Attention to detail is minute, with the exterior automatically illuminating at night as you approach, thanks to a sensor detecting the key in your pocket.

There is satellite navigation, an on-board computer and a screen diagram which shows how the electric and petrol engines are interacting, although to me it was nothing more than a pretty picture.

Parking is also easy, thanks to front and rear sensors and a colour reversing camera. There is plenty of room up front, although rear leg room was a little cramped and I thought the boot was small for the class of vehicle.

And the wood trim was a little garish, while there was far too much plastic on the dashboard, which detracts from the car's luxury status.

But ultimately, anyone will enjoy driving the Lexus. It is super smooth and the quality of the finish is second to none.

And when you back that up with Lexus's reputation for reliability, it is a formidable package.

And the accountants will love it too. It incurs a rate for company car tax of 21 per cent about the same as a two litre Ford Mondeo, which is a major bonus.

In the luxury car segment the combination of technology, refinement and value for money in the Lexus make it difficult to beat.

Jaguar and BMW beware.