Smart motorway construction firms were placed under investigation for fraud, bribery and corruption, it can be revealed.

Workmen for companies building the roads were accused of stealing scrap metal and submitting false claims for hours worked by creating ‘ghost employees’.

Investigators at National Highways found £320,000 of scrap metal was ‘unaccounted for and missing’ from a project on the M1, according to leaked internal documents.

But they were unable to pursue a criminal prosecution for theft due to a lack of ‘reliable witness testimony’ and ‘concerns for the safety’ of one witness.

They found ‘no evidence’ to support the ‘ghost employees’ accusation. These claims are part of a dossier containing bombshells, obtained by Daily Mail. It was prepared by National Highways road bosses.

The claims concern a section the M1 smart motorway between Junctions 13-16, Milton Keynes and Northampton. This segment is due to open in late this or next year. After the claims, the agency claimed it withheld payments from construction companies.

Development of smart motorway at Junction 14 of the M1 between Milton Keynes and Northampton, which is due to open either later this year or next

The construction of a smart motorway between Junction 14 and 14 of M1 in Northampton is expected to be completed by the end of this year.

Among the accusations was also that one worker for the main contractor, a joint venture between Costain and Galliford Try referred to as ‘CGT JV’, was handed ‘brown envelopes’ on building sites by subcontractors, said to be in return for business favours.

The same worker, who was alleged to have benefited from the theft of scrap metal, was also accused of accepting ‘inappropriate gifts’.

National Highways investigators said that, although there was evidence cash-filled envelopes changed hands, it accepted the explanation that the money was for ‘staff parties’. The documents added that it could not find evidence to support the gifts claim, which involved the CGT JV worker accepting ‘a significant sum of money [from a subcontractor] to pay for a trip abroad to watch a football match’.

The claim could not be supported because the worker, who cannot be named, ‘produced receipts to demonstrate the trip was made at his own expense’.

Evidence was found to show that he bullied his colleagues, and he quit last year following being suspended.

National Highways investigators said that, although there was evidence cash-filled envelopes changed hands, it accepted the explanation that the money was for ‘staff parties’. Pictured: The scene after a crash in June 2019

National Highways investigators said that, although there was evidence cash-filled envelopes changed hands, it accepted the explanation that the money was for ‘staff parties’. Photo: A scene following a June 2019 crash

Costs for the removal of the hard shoulder on the 23-mile stretch had ballooned by more than 50 per cent from £297 million to £453 million.

Whistleblowers feared that contracts were being manipulated to line construction bosses’ pockets. National Highways disagreed and found that there was no evidence to support the price rises. CGT JV denied that the cost rises were due to these claims.

The papers concluded: ‘Our calculations suggest scrap metal to the value of £320,000 is unaccounted for and missing from the credits recorded.’ The report found that ‘on the balance of probabilities, National Highways has incurred a financial loss’. But a lack of ‘reliable witness testimony’ meant it was unable to prove the allegation of theft.

According to some reports, the worker who quit also made a profit from selling scrap metal along an older M1 stretch between junctions 16-19. National Highways was not able to investigate. Construction of the M1 J13-16 Scheme began in 2018. This is the sixth smart stretch, and it’s one that has been moving ahead despite eleven other projects being halted by Grant Shapps (Transport Secretary).

This was in response to a Commons Transport Committee report calling for corrective action regarding flaws that were blamed for causing several deaths.

Tory MP Karl McCartney, who sits on the Commons transport committee, said: ‘I believe these alarming allegations need more investigation.’ Pictured: Heavy traffic on the M1 'smart motorway' in Bedfordshire

Tory MP Karl McCartney, who sits on the Commons transport committee, said: ‘I believe these alarming allegations need more investigation.’ Pictured: Heavy traffic on the M1 ‘smart motorway’ in Bedfordshire

Separate papers also show that workers employed by the main contractor, Kier, for another scheme ‘manipulated’ tender processes, awarded a subcontract worth £1.4 million in breach of rules and that this was ‘influenced by bribery’.The claims were in relation to a stretch of the M6, junctions 13 to 15, also being converted.

The internal National Highways papers state: ‘Evidence found during this investigation supports the allegations made but is insufficient to identify individuals.’

Tory MP Karl McCartney, who sits on the Commons transport committee, said: ‘I believe these alarming allegations need more investigation.’ It is understood no formal police probe was launched.

National Highways smart motorways programme director David Bray said: ‘We investigated, working collaboratively with our contractors, the allegations around the M1 and M6 schemes and prevented the payment of any amounts that we were not fully satisfied with.’

And CGT JV said: ‘Both the CGT JV and National Highways investigations confirmed that there is no connection between any of the allegations and increased costs of the M1 junction 13-16 project.’

A Kier spokesman said: ‘In this instance, following a thorough investigation and report by National Highways in May 2020, we worked with an independent body to carry out a further internal investigation.

‘Both concluded that there was no evidence to support potential procurement fraud and bribery.’