Stormont Finance Minister Simon Hamilton has strongly rejected claims that giving the Executive powers on corporation tax is an economic gamble.
And Enterprise Minister Arlene Foster also voiced "disappointment" that a leading businessman warned politicians here may not be ready for the move.
But insurance firm boss Bro McFerran's concerns have been echoed by a former Northern Ireland minister, who warned the public will lose out if Stormont is given control to vary the corporation tax rate.
On the eve of an expected announcement by Chancellor George Osborne, Lord Kilclooney insisted the estimates it could bring 50,000 new jobs were "wishful thinking".
The former Ulster Unionist minister - best known for saying he would not touch a deal on offer during the Good Friday Agreement negotiations "with a 10ft barge pole" - also argued the go-ahead for corporation tax will mean "further large redundancies".
Lord Kilclooney, the former John Taylor, said: "Stormont has announced redundancies in education, hospitals and agriculture due to budgetary issues. There will be further large redundancies if Stormont opts for a 12.5 % corporation tax.
"It is time that the Ulster Farmers Union, the teachers' unions and the various health unions spoke up for their members before it is too late. They do not seem to realise the threat.
"Of course businesses will benefit by paying less tax, but the general public will be the losers."
The peer, who was MP for Strangford and a Policing Board member until the 1990s, said: "Some Stormont politicians are promising 50,000 new jobs if the tax is reduced, but this is only wishful thinking. There is absolutely no basis for this claim, yet many have fallen for it."
Mr Hamilton insisted, however: "I would not describe it as a gamble, (though) there are always risks involved in any policy decision."
He said when he examined the kind of measures available to the Stormont administration "there are none better than corporation tax in terms of the results it can produce".
Speaking on the BBC Nolan Show, he added: "We have a cross-party consensus at Stormont that we want to do this. It's not a gamble because I am convinced we will see employment in the private sector rising,"
Speaking in the Assembly, Mrs Foster said she had been disappointed by the comments of Mr McFerran, managing director of insurance company Allstate NI, who said on Sunday: "Our Northern Irish politicians need to show that they can deal and resolve the existing issues before they get into the realms of corporation tax,.
Mrs Foster said she was especially disappointed given that Mr McFerran's company had received funding from Invest NI.
"I hope that we get a positive announcement in the next few days," she added. "I believe that it will bring huge benefits. If we are going to have more jobs, people will have money to spend in our restaurants and shops."