"I think this is a binary, old-fashioned and reductionist definition of identity", the former Belgian prime minister told Irish politicians.
Mr Verhofstadt's outspoken attack is the latest to come from Europe about Mr Johnson's article, which got a bad reception on the continent where it was largely perceived to have a nationalist overtone.
Sinn Féin said last night its MPs will attend the address in the Dáil chamber.
"The sort of analysis we have published today with our colleagues in the Irish and Northern Ireland statistical agencies is going to be indispensable as these negotiations develop".
He added that the potential problems with the border were a "consequence of the decision of the United Kingdom to leave the European Union" and the "solution has to be proposed by the United Kingdom side".
Well, if May sticks to her current plans to leave the customs union, then there will need to be some form of new border controls between Northern Ireland and the Republic of Ireland, in order to avoid smuggling between the United Kingdom and EU.
"For the moment we don't see a workable solution being put forward by the United Kingdom government".
"But the point is the United Kingdom government has to come forward with a proposal that solves the problem", he added.
Verhofstadt's attack comes after the foreign secretary's Daily Telegraph article in which he said lack of allegiance to the country by some voters drove the leave result in the European Union referendum a year ago.
Verhofstadt's comments follow the publication of a position paper by the European Union, which pushed responsibility for solving the Irish border issue onto the UK.
Mr Verhofstadt said: "We feel, hopefully I am wrong, that we don't receive always a clear United Kingdom position".
But she added: "We will not countenance any customs deal that cuts Northern Ireland adrift from our primary marketplace".
"Whether it be in terms of transition or future trade relations with those in the single market, Northern Ireland must be treated in the same fashion as the rest of the United Kingdom".
Although he is not directly involved in the Brexit negotiations, any deal between the EU and United Kingdom will need to be approved by the European Parliament.
Verhofstadt, who spent Wednesday in Belfast meeting political leaders and the evening on the Irish border, said Ireland showed it was possible for multiple self-identification to co-exist and flourish.
People born in Northern Ireland are entitled to Irish citizenship, which means they could remain part of the EU.
UUP leader Robin Swann said after meeting the MEP that "special status for Northern Ireland is not an option".