The Assembly's main parties today face charges of "betrayal" if the Executive presses ahead with the introduction of water charges despite election promises made last year.
Opposition to the tap tax was a key issue on the doorsteps in last year's Assembly election, with the main parties vowing to fight proposals tabled by Peter Hain's direct rule team. But now in government, those same parties are due to finalise plans to levy household bills from April next year.
North Belfast Ulster Unionist MLA Fred Cobain commented today: "People will feel betrayed. If water charges do come in, they are actually being betrayed."
Water charges were deferred by the new power-sharing government last year and an independent panel was set up to examine the options.
Agreement at the Executive on the way forward would lead to a blueprint being issued for public consultation within the next few weeks.
The Department for Regional Development, headed by Sinn Fein Minister Conor Murphy, will be responsible for steering through the measure.
His party's manifesto for last year's Assembly poll listed "no water charges" as one of its priorities.
In an election platform article for the Belfast Telegraph in February 2007, Sinn Fein's Raymond McCartney wrote: "If we get a fresh, enhanced mandate Sinn Fein will go back into Stormont and block water charges at every opportunity."
The DUP's election manifesto said there "does not need to be a significant increase in the overall tax burden".
The UUP has called for a capping of bills at £100, while a " fairer, more sustainable" alternative was devised.
In its 2007 manifesto, the SDLP said: "The SDLP opposed water charges in Westminster and will continue to do so in the Assembly."
The new charges are scheduled to be phased in over two years. Next year, the average additional burden for households is predicted to be £160, rising to £250 in 2010.
The calculations will take account of the contribution households already make towards water services through rates.
This plan is in line with the independent panel's recommendation and is designed to address fears that people would be "double charged" for water.
UUP leader and executive Minister Sir Reg Empey last week called for a rethink on proposals before the Executive.
Mr Cobain is now heightening the pressure and warning that a tap tax will be opposed within the Assembly.
He claimed water charges could be a "financial disaster" for families on top of rising petrol, heating and food prices.
"There are people who just couldn't afford it. What about the Executive's promises on child poverty, pensioner poverty and fuel poverty? Where are they? Are they all out the window too? These are the people who before the last election were telling the electorate to say no to water charges. These are the people who were elected on this slogan."
The UUP man chairs the Assembly Regional Development Committee, but stressed that he spoke in a personal capacity.
Mr McCartney said: "If people read the Sinn Fein manifesto, they will be very clear as to what our position was. We said no to double charging, that there should be an end to the direct rule regime and that there should be an open, transparent debate on how we move forward. The independent panel was the way to do that."
On his 2007 article, he said it was referring to the "direct rule regime" which was preparing to privatise the water service.