In the latest of a series of problems to hit Metro C, which was first conceived in 1994, the board of Società Metro C, the company overseeing the works, said on Friday that further work was "untenable" due to "serious management breaches".
The board blamed "numerous serious administration errors, which have forced general contractors to, among other things, use their own resources to cover missing payments of over €200 million."
The issues had not been addressed despite persistent requests to the city's authorities, the board added in a statement.
"Roma Metropolitane and the city administration must answer to all this, not only to the general contractors but to the entire population."
A section of the line which runs in the east of the capital opened in November last year, but was immediately beset by problems, including late-running trains and malfunctioning doors and station escalators.
The line, which is expected to eventually be expanded to Piazza Venezia and the Colosseum, does not yet connect with the metro's other two lines.
But despite the many setbacks, the board said the line was having a positive impact on residents, with 6.2 million passengers so far being transported on the section that is open.
"The work - despite its current limited extension due to the ongoing lack of the financing necessary to create a link to the north-east quarter of the capital - has already produced a significant benefit for urban’ mobility."
The board also boasted about the trains' punctuality on the line.
"The service has a rate of regularity of over 99 percent - making it the best metro line in Europe for efficiency."
But most residents in the capital would not agree with this accolade. Rome has been beset by persistent transport woes, with strikes and delays an almost daily occurrence, and serious problems not uncommon.
In September, commuters on the Metro Line A had to be evacuated following a ceiling collapse, and in July, passengers were left horrified when a malfunction meant a train travelled between two stops with its doors wide open.
In the same month, a 5-year-old boy died when he fell into a lift shaft at a metro station. Three members of staff were later detained for manslaughter.