The European Parliament on Wednesday overwhelmingly adopted tough "red lines" for negotiations over a Brexit deal, on which EU lawmakers will have the final say in two years' time.

The parliament largely followed EU President Donald Tusk's draft guidelines issued last week after British Prime Minister Theresa May formally triggered the historic Brexit process.

But they omitted any mention of the flashpoint issue of Gibraltar, unlike Tusk's guidelines which said that Spain should have the final say over whether any eventual trade deal applies to the British outcrop.

The Strasbourg-based parliament is the first EU institution to formalise its stance on the Brexit talks, passing the resolution by 516 votes for, 133 against and 50 abstentions.

"You will set the tone for Britain," the bloc's Brexit negotiator Michel Barnier told MEPs just before the vote.

Parliament veto

The text insists that Britain must first make "substantial progress" on divorce terms -- the rights of three million EU citizens living in Britain, the exit bill and the fate of the border in Northern Ireland -- before striking a trade deal with the union.

It says that MEPs are prepared to accept a transitional deal to ease the effect of Britain's exit from the EU's single market in 2019, but that it should be limited to three years.

Barnier said the message on phased negotiations should be that "the sooner we agree the principles of an orderly withdrawal, the sooner we can prepare our future relations in trade."

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 during the two years of negotiations ahead of Britain's exit in March 2019.

European Parliament President Antonio Tajani called for MEPs to be fully consulted on the negotiations, given that they must ratify the eventual agreement.

"I would like to recall that any possible final deal must be cleared by this house," he said.

The remaining 27 EU countries will rubberstamp Tusk's guidelines at a summit on April 29, paving the way for Barnier to begin formal negotiations with Britain at the end of May.

Barnier wants a draft deal by October 2018 so that national leaders will have time to approve it before a ratification by the European Parliament, most likely in early 2019.

The resolution won the backing of all the major groups in the parliament, from the conservative European People's Party (EPP), the biggest bloc, to the Socialists and Democrats alliance, as well as the ALDE liberals, the Greens and the leftist parliamentary group GUE.

Parliament's Brexit negotiator Guy Verhofstadt said it was "key to have a united European Parliament together with the EU negotiator and the European Council," the forum for member states.

The EPP's leader, Manfred Weber of Germany, told the assembly that "we want a fair and constructive atmosphere," but warned that Britain cannot get a better deal by leaving the bloc, instead of staying inside.

'Mafia, gangsters'

The Brexit talks have already got off to a difficult start after London was alarmed by a clause in the Tusk guidelines saying Spain had to be consulted on any post-Brexit trade deal that affects Gibraltar, a British territory since 1713.

But no reference to Gibraltar was contained in the adopted resolution.

The territory's Chief Minister Fabian Picardo said he had spoken repeatedly in recent days to Britain's Brexit minister David Davis, who reassured him he would "not allow himself to be bullied into accepting inferior treatment for Gibraltar".

Gibraltar Wednesday accused Spain of causing long traffic jams with tightened border controls, saying it was "clearly a response" to rising political tensions over the rocky outcrop at Spain's southern tip.

Besides Gibraltar, Brexit champion Nigel Farage compared the EU to the "mafia" that was taking Britain "hostage" by demanding a multibillion-euro exit bill.

Several MEPs jeered Farage over the comments, and Tajani, who is from Italy, called his mafia remarks "unacceptable."

In response Farage fired back: "I do understand national sensitivities. I will change it to gangsters."

But Verhofstadt, a former Belgian premier, predicted that a future generation of young Britons would seek to rejoin the European fold.

That generation will "see Brexit for what it really is, a catfight in the (British) Conservative party that got out of hand."