Boris Johnson says Northern Ireland will not be hit harder than other regions in the UK if it votes to leave the EU.
Speaking during a visit to Boomer, a Lisburn firm which makes parts for Wrightbus, he said:
"The impact is either neutral or positive. I've looked at some incredible businesses here in the last few hours."
Asked how is campaigning for the UK to leave the EU, despite a recent poll suggesting 81% of businesses in Northern Ireland are pro-Europe he said:
"I think everyone is based towards the status quo.
"Project Fear is going on by the Government who are trying to scare the pants off everybody. I don't think that's the case (that we would be worse off)."
But he dismissed fears Northern Ireland would be hit hardest of there was to be a Brexit.
"No. I think the whole of the UK has a real chance to different deal and to remain very close trading partners (with Europe)."
"There's a big chance for a better arrangement on fisheries, on farming and on free trade deals around the world."
The Mayor of London made the case for leaving the EU as he visited the Wrightbus factory in Antrim to officially announce a Transport for London order for 200 more of its famous Routemaster red buses.
The deal, which is worth £62 million, will sustain 300 jobs at Wrightbus and will take the number of Routemasters on the streets of London to 1,000.
Mr Johnson's visit to Northern Ireland came 48 hours after Prime Minister David Cameron travelled to the region to make the case for staying in the EU.