Annual financial results at Merlin Entertainments were overshadowed by the disclosure that the firm is to be prosecuted by the Health and Safety Executive over last summer’s Smiler rollercoaster accident at Alton Towers.

Two female passengers on the ride suffered leg amputations and three others were also seriously injured when their carriage collided with a stationary carriage on the same track.

Merlin Attractions will appear at North Staffordshire Justice Centre, Newcastle-under-Lyme on April 22 to face a charge under the Health and Safety at Work Act.

Neil Craig, head of operations for HSE in the Midlands, said: “We have today [told] Merlin Attractions that it will be prosecuted for breaching health and safety law.

“This was a serious incident with life-changing consequences for five people.

“We have conducted a very thorough investigation and consider that there is sufficient evidence and that it is in the public interest to bring a prosecution.”

The accident in June led to a 12.4% slump in like-for-like sales in the group’s resort theme parks division as poor trading at Alton Towers spread to Thorpe Park. The divisional operating profit was down by more than £40 million year-on-year.

“The performance of the operating group was dominated by the impact of the incident at Alton Towers and the resulting significant decline in park visitation through the main trading season,” Merlin said.

“Whilst the majority of the impact was experienced at Alton Towers Resort, this created a difficult day-visit theme park market across the UK. As a result Thorpe Park, our other major rides park, also experienced a decline in visitation.

“Action was taken to limit the decline in volumes and refocus marketing efforts towards younger families and the broader short break appeal of the resort. However, this had limited effect over the key summer trading period in the face of ongoing media coverage of the incident.”

Chif executive, Nick Varney, said: “Despite a challenging year, the business delivered a robust performance in 2015.

“We continued to see a strong trading performance in Legoland Parks and a positive contribution from new business development, opening seven new Midway attractions and expanding our accommodation offering with the addition of 277 new rooms.

“However, 2015 was a difficult year for Merlin following the accident at Alton Towers early in the summer season.

“The safety of our guests and employees must always come first and we have sought to learn every possible lesson to help ensure there is no repeat of what happened on June 2.

Overall pre-tax profits nudged up by 0.3% to £2450 million for the year to December 26 although underlying earnings [EBITDA] fell by 4.3% to £402 million as revenues rose by 0.4% to £1.28 billion.

Total visitor numbers were up 0.3% to 62.9 million.

Varney said: “Merlin has a clear strategy, with clear competitive advantages leaving us well positioned in a dynamic marketplace.

“We have announced our new business development milestone targets for 2020 including 2,000 new rooms, 40 new Midway Attractions and four new Legoland parks.

“Whilst we remain mindful of macro-economic and geo-political factors outside of our control, we remain confident in the strength of the underlying business and the natural diversification that the growing portfolio creates.”

The company also revealed that it was acquiring a 15% stake in tourist ‘hop on hop off’ city tours business Big Bus Tours for almost £25 million. The company operates in 17 cities.