Two firms have been fined a total of £7,000 and ordered to pay £12,318 costs after part of an office block fell and crushed a worker’s leg.

The collapse was the result of a load-bearing pillar being constructed on the suspended precast concrete ground floor, instead of being taken down to a foundation.

The Health and Safety Executive (HSE) prosecuted the building’s designer, Peter Wallace of the Wallace Partnership, and the principal contractor, Jack Smith (Builders) Ltd, following the collapse at Kirkham Crossroads in Preston.

Blackpool Magistrates Court heard that emergency services, including Lancashire Fire and Rescue Service’s major incident unit, were called to the scene on 14 October 2008.

Peter Wallace, managing director of Wallace Partnership, said: “I have worked with Jack Smith Builders on a small number of schemes over the past 15 years with no problems. However, the haste with which this construction was undertaken meant that this project was being designed as it was being built, leaving little or no time for reviewing past information.

“This particular pillar was shown on several of our drawings but omitted on one. We were employed as designers on this project, not to inspect the works. I visited the site only when requested to answer specific queries – 8 visits in 6 months – and was never asked about this particular pillar.

“I deeply regret my part in this accident and am very sorry for the pain it has caused Mr Meeks and his family, and wish him well for the future.”

Allen Shute, the investigating HSE Inspector in Lancashire, said: “One of the workers’ legs was badly broken after the rubble fell on him, but the consequences could have been much worse.

“This was a basic error which should have been spotted by both the building’s designer and the principal contractor.

“It is common sense that the pillar supporting the floors should have gone into the foundations, and not just rested on the floor below. It’s vital companies learn lessons from this to prevent similar incidents happening in the future.”

Peter Wallace of the Wallace Partnership, of Pope Lane in Preston, pleaded guilty to breaching Section 3(2) of the Health and Safety at Work etc Act 1974. Jack Smith (Builders) Ltd, of Cottam Lane, Ashton in Preston, pleaded guilty to breaching Section 3(1) of the Health and Safety at Work etc Act 1974.

Both charges related to the safety of workers being put at risk. Peter Wallace was fined £4,000 and ordered to pay £12,318 towards the cost of the prosecution at Blackpool Magistrates’ Court on 12 May 2010. Jack Smith (Builders) was fined £3,000 with costs of £12,318.

Jack Smith builders declined to comment.