The three best "plan B" alternatives to the Government's €3bn national broadband plan will cost more, take longer to put in place and leave up to half of households without high-speed internet access.
Government officials drew those conclusions in a 28-page Department of Communications document shared with the Department of Public Expenditure earlier this year.
According to the 'Contingency Plan Report 2019, Comparative Table', which was published this afternoon alongside 23 other documents, if the broadband plan was scrapped three alternatives are available.
They include a "phased approach" roll-out of the scheme, a "separate build" approach which would see two separate tenders, and a "back haul only" scheme which would focus on "selected locations".
In each case, the officials concluded the alternatives pose too many problems and should not be considered.
The contingency report said the first option - a phased approach - would see a contracted firm develop 300 connection points "within two years" and another 1,000 connection points "within circa four years".
High-speed broadband would then be provided to 26,000 premises for each of the two stages, before expanding the service further.
The contingency report said the areas to be targeted would be chosen based on "socio-economic" and other reasons.
However, while this would give officials greater control of budget levels and "likely" stay within State aid rules, it would only ensure 52,000 homes are connected by mid-2023 "with uncertainty on when remaining premises will be addressed" and fears "the urban-rural digital divide will increase over the duration of this project".
The report said the second option - a "separate build and operations contract" with a €1bn budget - would create 300 broadband connections within two years and 1,000 within four.
However, the report said "internal modelling" has suggested "24% [127,000 premises] of the current intervention area would be covered under this option".
In addition, it said option two would mean a "network contractor would avoid deploying networks towards the more expensive premises in any given area" and would focus on those that are "easiest to reach".
The third "plan B" option - a "back haul" approach - was also downplayed in the report, with officials arguing that subsidising the roll-out of fibre backhaul to selected locations will mean "many premises will fall outside of this range".
"The majority of premises would not receive the service and this type of intervention would not meet the Government's objectives," the officials found.
The contingency report also said that while there was interest in asking the ESB to take up responsibility for the broadband roll-out, the attorney general Seamus Woulfe "has advised that significant legal risks" come with such a move, in particular in relation to State aid law.
The report said any broadband alternatives must be cost-assessed and future-proofed, and that there is merit to establishing a new broadband agency to oversee the project.
However, if this project is to be up to scratch, the officials said between 20 and 30 expert staff specialising in economic, financial legal, technical and regulatory matters will be needed.