Irish Water will need €120m from the exchequer this year because of a funding shortfall due to the proposed suspension of water charges, according to a briefing document prepared for Minister for Housing, Planning and Local Government Simon Coveney.

The document said this will be somewhat offset by a suspension of the water conservation grant in 2016, but will add €115m to taxpayer costs for the improvement of water services in 2017.

Irish Water has outlined a €5.5bn programme required to bring the country's water system up to an acceptable international level by 2021.

The installation of 820,000 meters nationwide has led to the saving of 32m litres of water every day because of leak detection.

The operation of the metering programme is currently under review "in light of the confidence and supply arrangement".

The document said legislation to facilitate the suspension of charges will have to be introduced within six weeks of government being appointed and will also have to establish an External Advisory body to build public confidence in Irish Water.

The document also warned that the European Commission "is concerned" about outstanding gaps in implementation of the Water Framework Directive and intends to escalate infringement proceedings if "early progress" on legislation is not achieved on the operation of the overall water system including providing safeguard zones around drinking water.

The document, published last night on the website of the Department Of the Environment, said the "overall mix" of financing for Irish Water in the future will be dependent on the outcome of the Expert Commission and the Oireachtas process in relation to domestic water charges.

A separate briefing document on housing said total investment in housing for this year is projected to be at €933m.

This will be based on exchequer transfers from the department to the social housing sector, and funds being retained by local authorities from the property tax.

The document revealed 80% of Local Property Tax funding is being retained locally for services.

The department hopes to progress some 5,000 units already funded and for which projects are close to, or have already begun, saying there is an overall target of 17,000 social housing units.

It also said one source of funding has fallen recently; the plastic bag levy collected €13.6m in 2014, falling to €12.1m in 2015 as people use less bags.