An ultra-exclusive sports car named after a Roman siege catapult is being unveiled by Midland niche manufacturer GTM today.

Only 15 of the Ballista two seaters will be built by the Coventry firm this year in an effort to maintain the brand's cache.

The 150mph marque is the first car to be produced by GTM which can only be bought in completed form.

Its earlier Libra and Spyder models can both be purchased as kits as well as completed versions - the firm has sold 450 to date.

The Ballista will be shown at the Autosport 2006 show which begins at the NEC today.

David Keene, managing director of GTM, said the car was aimed at people who wanted something different.

His company has been working for a year on the new model.

Mr Keene said: "We wanted something striking sounding. Ballista sounds like something fast, and from this word comes the term ballistic which is related to bullets."

The new car will be able to accelerate from 0-60 in 3.8 seconds and is powered by a 3 litre Duratec, V6 engine, producing 220 bhp and weighing in at 600kg.

Its enormous power-to-weight ratio is achieved through the incorporation of a tubular frame chassis with choice of a glass or carbon fibre skin.

A racing braking system, 18 inch split rim alloy wheels, an extremely rigid chassis and suspension system will help to manage the car's performance, Mr Keene said.

New owners will be able to select from a wide range of colours for the exterior and interior finishes, while the car will come equipped with a six speaker stereo sound system, satellite navigation and the latest Auto-txt vehicle tracking and security system.

Mr Keene said: "We are very excited with what we have achieved with the Ballista.

"It is an uncompromising sports car that looks great and delivers an awesome driving experience.

"We will only produce 15 of these a year, in order to create a halo effect, a bit of a buzz around the rest of the range.

"But we anticipate increasing the numbers considerably in subsequent years."

GTM anticipates that it will create a new niche in the market, offering the power, excitement and prestige of sports cars in the £40,000 to £70,000 range, at a more accessible price.

Mr Keene said: "There will not be many out on streets, so they will definitely turn heads, but at a fraction of the cost of Ferraris and other sports cars.

"Every one will be different and built to the customer's specifications."

The Ballista will be able to drive on the road and be easily convertible for people who want to take it racing on track days, Mr Keene said.

It will be produced at GTM's factory on the Bilton Industrial Estate, and represents part of GTM's attempts to join the car making mainstream.

Mr Keene added: "Companies like TVR and Noble started out as making kit cars before becoming low volume specialist sports car makers.

"We are now trying to lift everything and push on from kit cars to that area.

"At the moment we make about 50 cars a year, but by the end of 2008 we want to be making about 200."