Social Development Minister Nelson McCausland told MLAs that rejection of the Welfare Reform Bill would entail "huge costs", on 9 October 2012.
It would, he said, result in "less money for schools, less money for health, less money for the police".
Before the debate on the second reading commenced, the Speaker, William Hay, had warned members that if an amendment was passed at this stage the bill would fall.
Mr McCausland described it as one of the most important bills on the Assembly's history, and said there was a need for a welfare system that was fit for purpose in good times and bad times .
He said there were 120,000 households in Northern Ireland where no-one was working.
The minister outlined the four main principles of the bill.
These were: protection of the vulnerable, support and encouragement to get people involved in economic activity, fairness, and personal and social responsibility.
Mr McCausland said the current, highly complicated benefits system deterred some people from seeking work.
"In the changes that are proposed work will pay," he added.
The minister outlined what he saw as the benefits of the new Universal Credit.
"Universal Credit will lift 10,000 children out of poverty," he said.
Mr McCausland said a cap would be imposed on benefits.
Unemployed people "should not be receiving more than the average income. This is a matter of fairness," he explained.
The minister said Universal Credit would bring an additional £110m into Northern Ireland.
Mr McCausland again rejected the suggestion that the bill could be deferred.
"If we defer this there is no road left," he said.
The minister said deferral would ultimately result in a deficit to the Northern Ireland budget of £200m.
He said there were serious implications for the most vulnerable people in Northern Ireland.
Sinn Fein's Mickey Brady said his party's amendment was "not about killing the bill".
The amendment called for the second stage not to be passed to allow time for "further consideration and adjustment to better reflect the specific circumstances, obligations and needs of our people".
Mr Brady said all parties in the house had expressed concerns about the bill, and these were "Tory policies from Westminster".
He said the proposals were not about tackling poverty but about attacking the poor.
The debate continued after Question Time.
You can read about the second part of the debate