NI's First Minister Peter Robinson has condemned NI Water's response to the ongoing water crisis.
Speaking after an emergency Executive meeting called to discuss Northern Ireland's water crisis he said "someone had to be held accountable".
More than 6,000 homes remain without running water and NI Water is rotating supply to some 60,000 customers.
Mr Robinson said NI Water's response was "shambolic" and "ineffective".
He said he did not think anyone could suggest that the organisation had "covered themselves in glory".
"People must assess their own position and of course if people don't assess their own position the (Executive's) review will look at where responsibility lies and decisions will be taken on the foot of that," he added.
He went on to criticise the response of NI Water to the issue of water shortages.
Mr Robinson said: "It isn't simply a case of under-performing, we believe it has been shambolic at stages, it has been ineffective. It has not been the kind of organisation that is fit for purpose.
"If there has been a consistent feature from every minister, it has been their abhorrence at the treatment of customers by NI Water."
Deputy First Minister Martin McGuinness said NI Water's performance had been "totally unacceptable behaviour by an arms-length body".
He said it was "disturbing" that people at a senior level at the organisation had not anticipated the scale of the difficulties presented by the recent thaw in temperatures.
"We are not prepared to accept this treatment on behalf of citizens. Arms-length bodies need to be held to account," he said.
"Under no circumstances are we going to stand here and make excuses for a body that has failed so miserably."
He said it was a "key priority" that schools and businesses would be able to resume after the Christmas period.
Regional Development minister Conor Murphy said the board of NI Water was meeting on Friday and he was seeking an assurance that it would take "immediate steps" to ensure a similar situation was not repeated this winter.
Earlier, NI Water warned it could be next week before all homes and businesses are reconnected.
It said the numbers of those on a curtailed supply will vary from between 3,500 to 60,000 at any given time.
Those people on curtailed supply will generally find their supplies will be off for between six to eight hours.
In a statement on Thursday evening, the company said: "NI Water will continue to rotate supplies so figures will increase and decrease as this process is continued in order to protect reservoir levels.
"The figures for those without water will continue to decrease as bursts are repaired."
South Tyrone Hospital, Dungannon, and Lagan Valley Hospital, Lisburn, have been affected by the water supply crisis.
The Northern Ireland Secretary of State has warned there could be major changes in how the NI water supply is financed.
Owen Paterson said Northern Ireland's infrastructure had suffered over the years and that changes were now needed.
"What will be looked at here is the difference in the way that water is paid for in the rest of the UK and the way it is paid for in Northern Ireland, where it is just an element of the rates," he said.
"I think what is clear is that the events of the last week or so will bring this to a head. It is a major issue that has to be resolved."
Meanwhile South Tyrone Hospital has been relying on the NI Fire Service and bottled water. Lagan Valley Hospital was without water for a number of "hours".
Eighty villages and towns have been affected as pipes burst in the thaw.
Around 18,000 customers are still affected in the Belfast area, 5,000 in the eastern part of Northern Ireland and 8,000-9,000 in the western area.
Trevor Haslett, director of engineering at NI Water, said the situation in urban areas was improving and should be better by Friday afternoon.
However, he added: "It could be early next week before everybody is on supply."
Mr Haslett said over a period of 12 hours the company suffered more burst service pipes than he could remember for 35 years.
The company has invested £150m in water mains over the past three years, replacing 1% of the system but in other parts of the UK almost double the amount of infrastructure had been replaced, he said.
"If NIW received more money for water mains we could increase the rate of renewal," Mr Haslett said.
The company has admitted that substantially more people have been affected over the period of the shortages.
It said much of the extra 250m litres it has released into the system has already leaked out - some of it through its own own distribution system, but most because of damaged pipes on private property.
The Stormont Executive is currently discussing what further measures can be taken.
One man queuing for water in east Belfast said his water service has been interrupted since just after Christmas.
"It is just terrible, having to queue for water. It just should not happen," he told the Associated Press.
NI Water, a state-owned company, which is the sole provider of water and sewerage services in Northern Ireland, said an unprecedented number of leaks caused by the thaw following the long period of freezing weather had been putting "big pressure" on its systems.
The thaw followed the worst snow in Northern Ireland in 25 years and record cold temperatures.
As temperatures rose, burst pipes drained reservoirs, forcing NI Water to turn off the tap to the 80 locations.
Some people have been without water for 12 days.
The Stormont Executive has accepted help from Scotland and sent civil service staff to help out at NI Water's call centre.
Local councils are working to supply water and offer free showers to people without a mains supply and information is being provided on the NI Water website.
In a statement, the Utility regulator said the priority for the rest of this week was to let NI Water manage and restore supplies as a matter of urgency.
"We have asked for a meeting with NI Water early next week to discuss the company's performance," a spokesman said.
Meanwhile, North Down Alliance Councillor Andrew Muir has called on NI Water to halt its plan to sell reservoirs across Northern Ireland, including six in Craigantlet Hills between Bangor and Belfast and one in Groomsport at Portavoe.
He said that, in light of recent events, NI Water must scrap these sale plans.