Specialist contractors raised the alarm about the new scheme with three of the sectors’s main trade bodies as the first bills landed on their desks at the end of January.

Now specialist contractors are calling for independent monitoring to ensure the controversial FFI scheme is being operated fairly.

They also complain there is no public definition of what is deemed a material breach, which triggers the HSE cost recovery fees of £124-an-hour.

Chief executive officer at AIS, David Frise said: “I believe it is right that those who break the law should pay their fair share of the costs to put things right but I am uncertain as to how fair the system is – what exactly constitutes a material breach serious enough for HSE to notify in writing?

“It appears to be highly subjective and open to the interpretation of the inspector. Realistically, if you look hard enough you are likely to find a breach of HSE regulations on most sites.”

Members of the association claim HSE inspectors are ignoring main contractors and heading straight for specialists, who they fear are seen as easier targets because they do not have the same firepower to challenge inspector’s rulings.

The Fee for Intervention scheme has been introduced to recover costs from companies caught breaking health and safety laws. But firms fear it could fast turn into a revenue raising exercise.

In an unprecedented move, the Association of Interior Specialists has linked up with fellow interior sector trade bodies, the National Association of Shopfitters and Federation of Plastering and Drywall Contractors to raise these concerns with HSE officials.

Robert Hudson, NAS director, said: “The corner stone of this legislation is the term ‘material breech’.

“How can we advise our members on a strategy of compliance when the HSE are unable to provide a definitive explanation?

“To the untrained eye, it would appear to be a licence to print money. The industry needs firm and friendly guidance, not the subjective judgement of an inspector looking to raise another invoice.”

Interim director at FPDC, Steve Halcrow said: “Health and safety is of paramount importance on any construction site and we’d support any improvements in its implementation.

“However, we are concerned that the current proposals to adopt the FFI scheme could unfairly penalise specialist subcontractors.

“It is essential that a clear set of guidelines outlining what is required is put into action by the HSE.

“The HSE also needs to ensure probity as we see the need for an independent third party to monitor the scheme and ensure it is applied fairly and avoids being seen as tax to generate income.”

A spokesman for HSE said: “The construction industry is a high risk sector and HSE is focusing on high risk and poor performing sectors with fewer proactive inspections for businesses in lower risk areas. FFI will not influence which businesses we inspect.

“Individual inspectors do not have cost recovery targets. Enforcement decisions are made within published and longstanding frameworks which are subject to line management checks, peer reviews and internal audit to help ensure consistency.”

The HSE added that an Enforcement Policy Statement and Enforcement Management Model, together with examples of material breaches, could be found in the guidance for businesses on FFI available on HSE’s web site.

The spokesman said: “The Government and HSE believe it is right that those who break health and safety law, and not the public purse, should pay the costs incurred in making them put matters right.

“The many businesses that comply with their legal obligations will continue to pay nothing.”

Anyone receiving an FFI invoice will have 21 days from receipt in which to query it, should they believe they weren’t in material breach of the law or the time the fee is charged for is incorrect.

If they remain unhappy after the HSE’s response they will then have a further 21 days in which to lodge a dispute.