The German MEP mocked British parliamentarians for having to demand a vote on whether Britain should remain in the customs union after Brexit.
Mr Brok took a dig at what he called the “mother of all Parliaments”, putting into question the amount of power wielded by British MPs.
Talking to students at Cardiff University he said: “As a student, I was always proud to be in a country which was the motherland of democracy.
“In my living room, I still have a painting of the House of Commons I bought during my time in Edinburgh and I always said that is the powerful mother of Parliaments.
“In Brexit times I have learned that the European Parliament (EP) had more power than the House of Commons.”
Mr Brok, who sits on the Brexit Steering Group with Guy Verhofstadt, also warned Britain not to underestimate the role the EP will play at the end of the Brexit negotiations.
He continued: “They had to fight for an extra vote to get rights on the customs union question.
“It is in the treaty of the European Constitution, so to say, that the European Parliament has the last say on both the withdrawal agreement and the final agreement. If we say no, it’s no.
“The Commission or member countries together cannot overthrow the position of the European Parliament on this question. I think this should be taken into account.”
On April 26 MPs approved the non-binding motion, which called on the Government to include as an objective in Brexit negotiations the option of establishing “an effective customs union” between the UK and EU, without a vote.
The, or a, customs union is one of the main flashpoints in the debate over Britain’s impending exit from the EU and Brexit campaigners are sensitive to any suggestion that Britain might stay in such an association with the bloc.
Downing Street has played down the significance of the vote, saying it was a “routine backbench business debate”.