Michel Barnier said he had only repeatedly met with Mr Corbyn as part of his “open door” policy with interested senior figures, pointing out that he had also met with Nigel Farage and other leading eurosceptics.
The top Commission official said he that the “only person” he was negotiating with was Theresa May and that he had made this clear to the Labour leader “every time I’ve met him”.
“On Jeremy Corbyn, my door is open, it’s open to everybody,” he told reporters at a press conference in Brussels.
“I even met Mr Farage the other day, which was a very stimulating discussion. Mr Corbyn is an important figure in British political debate and he asked to meet me and I had no reason not to meet him. I can tell him where we stand.
“But I’m not negotiating with Jeremy Corbyn. The only person we’re negotiating with is Theresa May, and Davis Davis, and the British government. I made this very clear to Jeremy Corbyn at the beginning and I’ve said that to him every time I’ve met him.
“I want to listen to everybody to fully understand what’s happening in the UK, I want to take the time necessary to understand and respect the British political debate.”
Mr Barnier was questioned about his meetings with the Labour leader after a report in the Daily Telegraph newspaper, based on leaked minutes of one of the meetings, that Mr Corbyn had said he was open to the UK staying in the customs union.
Commenting on the memo, Mr Corbyn’s office said: “Jeremy did not say he was open to staying in the customs union. He said that a customs union was a viable end point.
“We have been clear all the way through that you can't be in the customs union if you are not in the EU.”