Watchdogs issued provisional findings in April following a competition probe into the groundworks market.
Officials have been investigating M.G.F. (Trench Construction Systems) Ltd, Vp plc and Mabey Hire Ltd.
Vp confirmed the provision in its preliminary results for the year to March 31 2019 which were released today.
It said: “The CMA announced on 9 April 2019 that it is investigating three major suppliers of groundworks products to the construction industry.
“The CMA has provisionally found that the three businesses, including a part of the Group’s excavation support system business (Groundforce), were involved in suspected anti-competitive behaviour.
“The CMA’s findings are, at this stage in its investigation provisional and do not necessarily lead to a decision that the companies have breached competition law. We continue to work on our response to the CMA’s findings.
“At this point in the process we cannot make an accurate estimate of the likely cost that may subsequently arise in the event that the CMA were to decide in the future that a breach of competition law has taken place.
“However, accounting standard IAS 37 requires us to provide an amount in these accounts and accordingly we have included a figure of £4.5 million as an exceptional cost.
“This figure is in the arithmetic midpoint of a range of possible outcome (£0 to £9.0 million) that we have calculated based upon previous cases and CMA published guidance and without any admission of culpability.”
Vp posted a strong set of results showing pre-tax profits up to £46.8m from £40.6m last time on turnover up to £382.8m from £303.6m.
Neil Stothard, Chief Executive of Vp said: “Vp has started the new financial year positively and in line with our expectations.
“We anticipate that our main markets in the UK will continue to be supportive, but with slightly slower overall growth than experienced in recent years influenced by the current political and economic uncertainty.”