A teenage worker at one of Scotland's busiest theme parks was in a serious condition in hospital last night after he plunged about 80ft from a rollercoaster ride.

The 18-year-old ride operator, who has not been named, had been carrying out repairs on the Twist and Shout ride at Loudoun Castle Theme Park in Ayrshire yesterday morning when he fell.

Members of the public looked on as he was treated by paramedics from the Scottish Ambulance Service, who arrived on the scene within minutes.

The teenager was then taken to Crosshouse Hospital, near Kilmarnock, where medical staff last night described his condition as "very serious".

Henk Bembom, director of the Loudoun Castle Theme Park in Galston, confirmed that the Health and Safety Executive has been informed and is investigating.

He said: "We are all devastated and extremely distressed and our thoughts are with our colleague and his family at this time."

Although the ride was not being used when the accident happened, the park was open for business and filled with adults and children.

A statement from Strathclyde Police said: "The man was working as an operator at the theme park and was carrying out repairs on the rollercoaster when the incident occurred."

The Twist and Shout attraction has been operating since 2003. It can carry up to 1500 people per hour, taking them 60ft in the air. Travelling at a top speed of 41mph, the ride has been voted one of the top 20 in the UK by a rollercoaster website.

In November last year, 18 people were trapped upside down for up to two hours in a fairground ride at Strathclyde Park in Motherwell. This followed a similar incident in 2002 at the same park when 11 people were trapped 100ft in the air for an hour.

At the UK's most popular theme park, Alton Towers in Staffordshire, 29 people were injured last year when two trains rides crashed.

Loudoun Castle Theme Park, which opened as an amusement park in 1995, is set in 500 acres of parkland around the ruins of a 19th century castle.

After going into liquidation in 1998, the theme park was bought by Henk Bembom's Parkware company in 2002.

According to reports, Bembom invested £5m in the park in its first year and a further £2m in 2003 and this year.

The Twist and Shout ride at the centre of the Loudoun Castle incident was previously located at Camelot Theme Park and Dreamland Margate.