The Government has been warned of serious risks to children and child protection services by Tusla, the National Child and Family Agency.

In an unpublished briefing document to Cabinet, seen by RTÉ's This Week, Tusla warns that children at "serious risk" are in danger of "serious harm".

It says the agency is "in default of its statutory obligations" due to the pressure being placed on child and family support services.

The document, which was presented to the Cabinet Sub-Committee on Policy and Public Service Reform chaired by the Taoiseach, lays out in stark terms Tusla's inability to meet agreed standards for all children referred to the agency and warns of more children needing more costly high-support services if investment is not made in early intervention.

Further funding cuts to services provided by community and voluntary sector will also have to be made if the Agency's funding is not increased, the paper warns.

Such organisations provide Tusla with rape crisis, domestic violence and family support services.

The briefing paper calls for €19.4m to be invested over a three year period to fund cases where children and families have no allocated social worker.

A study conducted by Tusla found that there were 8,865 such cases in 2014, of which 1,731 were classified as "high priority".

Half of all high priority cases had been waiting more than three months for an allocated social worker, far in excess of the recommended 21 day timeframe.

As a result of the pressure on social work services the Agency is "carrying a significant level of known and unknown risks to children".

Both the Department of Children and Youth Affairs and the Tusla say that emergency cases are dealt with, where there is an immediate risk to the life of a child.

However, the document warns that children who are in "serious risk" may become emergency cases if resource needs for early intervention are not met.

Under the heading "Risks", the document warns:

"Children at serious risk are not being identified in a timely manner and this can result in serious harm to a child and/or greater public expenditure later.

Children requiring a support service are not being diverted to more appropriate services and as their circumstances deteriorate, their needs are not being met.

Children may later access child protection investigations, mental health services, detention or special care when earlier more cost effective interventions would have prevented this.

Tusla projects that increasing pressure will be placed on services with mandatory reporting aspects of Children First child protection legislation, which is currently before the Oireachtas.

Child protection and welfare referrals to State child and family services have more than doubled in the three years from 2011 to 2014 from 21,000 to 43,000.

The Department of Children and Youth Affairs has echoed Tusla's concerns in its own internal risk register, which was released to This Week under FOI.

The register warns of a risk that "Children First legislation will be partially or poorly implemented" and "implementation of the mandatory aspects of Children First would lead to an increase in pressures on the child protection system, impacting on children and affecting public confidence in the child protection system".

Prior to Budget 2015 the Tusla Chief Executive Gordon Jeyes said the Agency would need €45m to keep services at a "standstill" level.

The Agency's 2015 budget allocation was increased by €26m to €635m.

The children's charity Barnardos has previously estimated Tusla was underfunded by €50-60m at its foundation.

The cost of legal services and guardians ad litem are among the Agency's significant costs.

Tusla's briefing document to Cabinet warns resources are also being diverted from foster care and family support into critical cases, resulting in greater risk to children and a higher cost to the State.

The cost of high-support residential services is €500,000 annually, according to the Agency, which it estimates is enough to provide an estimated 500 families with earlier parenting and family support.

The Cabinet Sub-Committee has been warned that Tusla cannot meet the shortfall in services from within current resources and staffing levels.

With current funding levels Tusla is in "survival" mode, according to the document and calls for investment to put the agency on a sustainable footing.

Half of all cost savings by Tusla to date have been made by slashing community and voluntary funding and the Agency warns further cuts would have to be made unless the its funding is increased.

In recent years Tusla has cut funding to services run by the Barnardos, marriage counselling, rape crisis and domestic violence support services.

Tusla, which was established at the beginning of 2014, moved child and family services out of the Health Service Executive.

However, the document calls for greater access to services which have remained within the HSE.

"Service pressure is exacerbated by ill-defined dependency on HSE Facilities and corporate support which understandably prioritises health service reform", the paper claims, highlighting the areas of ICT and Recruitment in particular.

"The case for investment for children services is not merely a morally compelling one but one that represents sound investment", the paper concludes.

Tusla's Chief Executive, Gordon Jeyes said there are around 5,000 children at risk.

Speaking on RTÉ's This Week programme, Mr Jeyes said the agency is not intervening in children's lives as early as they should, due to a lack of resources.

He said "We are managing that risk. Teams are monitoring it, they're looking at it, they're seeing if it changes but nevertheless there's a significant risk, because we are not intervening as early as we could."

Mr Jeyes said to meet demand, the agency would need around €132m over a three year peroid.

Minister for Children James Reilly has said is well aware of the concerns expressed by Tusla.

In regard to the issue of unallocated cases, Minister Reilly said he sought an audit from Tusla to establish the most accurate numbers on the issue.

The Minister further sought a business case from Tusla regarding necessary investment.