Delays to large-scale construction projects in the UK are now more than twice as long as they were before the pandemic, according to research from machine-learning start-up nPlan.

The report, which uses a dataset containing more than 500,000 construction schedules, found that projects undertaken since the pandemic began in March 2020 have a median delay of more than 200 days, or just over six months.

This compared with a 100-day average during the 15 years to February 2020, after records began in 2005.

The firm suggested the slowdown could thwart the government’s levelling up agenda, given the link between project delays and contractor insolvencies. Additionally, more delays could deter clients from starting new projects and erode trust in the industry.

Findings also showed that 45% of activities related to structural steel took longer than planned. Dev Amratia, chief executive of nPlan, said the additional pressure of steel shortages and delivery issues could create a “perfect storm” for contractors in the year ahead.

Data centres were more likely to be delivered consistently and on time than commercial buildings and infrastructure projects.

Overall, 85.5% of projects were delivered late during the past 17 years, with 13.4% delayed by at least a year.

Amratia said: “In construction, as in so many other sectors and areas of public life, the pandemic has not just created new problems, it has highlighted and exacerbated existing problems – in this case, the costly project overruns which are endemic to the industry.

“Because this issue was not dealt with before the pandemic, we are now in a situation where projects have suddenly become much riskier. This will pile pressure on contractors and may mean clients bring forward fewer projects.

“On the other hand, the salience the pandemic has given this issue means we now have an unparalleled opportunity to get better at anticipating and preventing project overruns using advanced forecasting and risk management techniques.”