Northern Ireland will be collateral damage during the British Government’s “collision course” with the EU, Martin McGuinness claimed.
The Sinn Fein leader claimed Brexit was driven by the internal politics of the Conservative party.
Prime Minister Theresa May has said her Government will begin exit negotiations with European counterparts next year.
Mr McGuinness said: “This British Government is embarked on a collision course with the European Union and this is happening at the behest of a very selfish approach.
“This is all about the internal machinations of the Conservative party and of course it appears that we are going to be the collateral damage in terms of politics and in terms of our economy in the time ahead.”
Northern Ireland voted to Remain in the EU by a 56% majority while the UK as a whole voted Leave.
Mrs May has said the UK will leave as one union.
Meanwhile, Stormont’s First Minister Arlene Foster said Northern Ireland could have greater flexibility in attracting foreign direct investment after Brexit.
European Union state aid rules limit the use of government incentives to encourage overseas businesses to establish offices in Northern Ireland.
Stormont ministers will also have the freedom not to charge householders for water after an exit, the DUP leader added.
Mrs Foster said she and Mr McGuinness were focused on achieving what is best for Northern Ireland, and will work with the UK and Republic of Ireland governments.
She added: “The deputy first minister and I have been very clear that we want to be directly involved in any negotiations so that we can put forward what is right for all of the people of Northern Ireland, regardless of whether they voted to Remain or voted to Leave, because what we are focused on now is what is best for the people of Northern Ireland.”
She said access to the single market was important but listed the benefits of leaving the union.
“If we were still members of the EU continuing, we would have to deal with the issue of domestic water charges, we would have to deal with the inflexibility in relation to attracting foreign direct investment.
“And also we would have to deal with state aid rules as well.
“The negotiations will be long, they will be protracted and we as a country should not be lacking in our ambitions.”