The sharp uplift was driven by the acquisition of May Gurney, but also saw the construction division benefit from early signs of a recovery in workloads.

Revenue in the first-half to the end of December jumped 47% to £1.43bn.

Even excluding May Gurney’s performance like-for-like sales were up 12% to top £1bn, with profits up a third at £30m.

Exiting chief executive Paul Sheffield said: “It is encouraging that the upturn in construction workloads observed last year has been sustained.

“Although margin pressure and cash generation will remain constrained as growth and inflationary pressures feed through the supply chain.”

The takeover deal and investment in housing and property saw Kier switch from a position of£60m net cash to net debt of £138m.

Sheffield said the construction division had managed to lift margins from 2.1% to 2.3%, even though there were early signs of upward pressure on costs.

He added: “Payment terms, particularly within the public sector, remain challenging.”

Cash fell from around £320m in the same period a year ago to £273m as shorter payment terms and the increasing proportion of infrastructure work with more irregular cash payments impacted on the business.

Sheffield said the services division had been transformed by the acquisition of May Gurney, which has cost Kier around £26m to integrate.

Kier’s combined business is now a £1bn a year turnover operation and is one of the market leaders in highways and utilities work.

More than £450m was secured in the six months, underpinning the £3.6bn order book and reflecting the seasonality of awards.

Sheffield said: “The integration remains on course, with good customer retention, new extended contracts and revenue synergies.

“We are on track to deliver the anticipated £5m cost savings in this financial year. The construction and property divisions continue to strengthen.

“As reported at the year end, we are seeing early signs of economic recovery across the country. Our wider portfolio of offerings, strong cost management, a growing order book of over £6bn together with our strong capital structure, position us well for the future.”