The firm said the latest hike in losses has been caused by issues at the building division.
It is the fifth increase in predicted losses as shares in nmcn remain suspended and talks continue over a refinancing deal.
Results for last year were due to be published in June but were delayed prompting the share suspension of the listed contractor.
Nmcn said on Wednesday that it is “continuing to work with its auditors to finalise the accounts for the year ended 31 December 2020.”
The update added: “Subject to completion of the audit, the Group is now expecting to report overall underlying losses before tax significantly in excess of the £24m indicated in the announcement of 28 May 2021.
“This will include both a material element which is attributable to 2019, and recognition within the 2020 Results (rather than in 2021’s financial results) of certain losses connected to the performance issues in the Group’s Building business unit announced on 14 June 2021.
“The Group had already reflected the majority of the increased 2020 Results loss within its existing internal working capital projections.”
Investment vehicle Svella revealed plans to take a controlling interest in nmcn following a £24m refinancing deal last month.
Lee Marks, nmcn Chief Executive said: “Since the announcement on 21 June of the recapitalisation, Svella has worked very well alongside the Company to progress the transaction and remain committed to ensuring that the recapitalisation is completed at the earliest opportunity.”
Nmcn added: “It is currently expected that the 2020 Results will be published during August 2021 at which point the Company will submit a request to the FCA and the London Stock Exchange to lift the suspension in the listing of the Company’s ordinary shares.”