The UK's non-papers do not meet the objectives of the backstop, Guy Verhofstadt has said.
Last week, the UK said it has shared with the EU a "series of confidential technical non-papers" which reflect its Brexit ideas, adding it will submit formal written solutions "when we are ready" rather than meeting an "artificial deadline".
The backstop - the contingency measure which would keep the UK closely aligned to Brussels' rules in order to prevent a hard border with Ireland - is seen as the main stumbling block to a Brexit deal.
The "non-papers" shared by the UK focus on the agri-food zone, customs issues and on manufactured goods.
Read More: No Brexit deal in sight, warns Michel Barnier
Mr Verhofstadt, the European Parliament's Brexit co-ordinator, said a meeting will take place in the European Parliament today to discuss "the non-papers or so-called alternative proposals that have been put on the table" by Prime Minister Boris Johnson.
He said: "They are not meeting the three conditions. This point is not solved and this backstop needs to be in place as it is for them. We have already said from day one that if they want to change the backstop, they can go to the one they first proposed because the backstop as it is now was at the request of the UK government."
"It was not the initial proposal of the EU side or whatever European negotiator. We wanted a Northern Ireland backstop only and also for the good reason that the majority of Northern Ireland voted against Brexit, so let's not forget that," he added.
Mr Verhofstadt was speaking at the first cross-party public hearing on Brexit in the European Parliament in Brussels today and had not originally planned to speak.
He said he wanted to respond to the various remarks made by people at the meeting who live and work on both sides of the border.
Mr Verhofstadt said he is opposed to a border on the island of Ireland and that "it is not just about avoiding physical infrastructure".
"It is also about the unity of the island economy. It's about the single market of the European Union. It's about the fallout of a border for the Good Friday Agreement," he said.
He said he visited the border shortly after being appointed as head of the steering group - "to look to a border that does not exist".
"Besides the fact that there are miles on one side and kilometres on the other side, and that the signs are yellow and white. That is the only difference that you can see," he said.
