"The sooner we agree the principles of an orderly withdrawal, the sooner we can prepare our future relations in trade," he told the European Parliament in Strasbourg.
"A free and fair trade agreement but also in security and defence," he told MEPs as they prepared to vote on the parliament's "red lines" for the coming two years of Brexit talks.
On Wednesday the European Parliament overwhelmingly adopted "red lines" for negotiations over a Brexit deal, including demanding Britain first agree divorce terms before striking a new trade deal.
The assembly in Strasbourg, France, which will have a final veto on any Brexit deal in two years' time, adopted the guidelines by 516 votes for to 133 against with 50 abstentions.
France's Barnier added that as the first EU institution to take a formal position on British Prime Minister Theresa May's letter triggering Brexit last week, parliament would set the "tone" for the negotiations.
The EU has rejected May's call in her letter for talks on the terms of the divorce and on a future trade deal to be held in parallel.
Michel Barnier. Photo: AFP
Barnier said Britain had to agree on terms including its exit bill, the rights of EU citizens living in Britain and the border in Northern Ireland before moving on to life after Brexit.
"We are not proposing this to be tactical or to create difficulties for the UK. It is necessary for the chances of reaching a deal in two years which is very short," he said.
He warned, however, that the "devil is in the details".
Barnier, a former European Commissioner and French minister, also urged the remaining 27 EU countries to stay united during the Brexit negotiations amid fears Britain could try to play on divisions.
"If the union is disunited we risk that there is no deal," he said.