Martin McGuinness has insisted there is no ambiguity in his party's stance in support of cutting corporation tax - but warned that a predicted jobs windfall linked to a rate reduction could be endangered by Brexit.
Rivals have accused Sinn Fein of double-speak on the political agreement to bring the rate down to 12.5%, claiming its position has wavered due to unease about the reaction of its voter base to a policy that would see millions cut from public spending to drop taxes for big businesses.
As the party outlined its manifesto, Mr McGuinness said cutting the rate to 12.5% by 2018 was based on it being affordable.
But he added: "I do think it will be affordable."
He said the reason he supported the move was because it could potentially create 37,000 jobs through new investment.
"The position is clear - there is no ambiguity in Sinn Fein's position. We, along with all the other parties, have signed up to a reduced rate of corporation tax of 12.5 % by 2018," he said.
But the Sinn Fein veteran claimed a Brexit could undermine Northern Ireland's ability to attract new investors to set up in the region.