The chief negotiator for the European Parliament (EP) urged the UK to trigger the exit talks as soon as possible and said negotiations should reach an end by 2019.

Liberal MEP Guy Verhofstadt told journalists Tuesday that he "cannot not imagine that we start a new legislative cycle without an agreement, and that we enter a new legislative cycle with no solution".

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The next EP elections will take place in 2019.

"The UK should trigger the Article 50 as soon as possible so that we can finalise these negotiations by 2019," Verhofstadt told a news conference in Strasbourg.

The liberal leader recalled that the EP needs to give its consent to the final exit agreement with the UK, that is why it is important that the EP is already part of the negotiations.

He said the EP's red lines in negotiations will be decided by the conference of presidents – group leaders and the EP president – and the EP's plenary.

The former Belgian prime minister warned London that the EP's position is that the UK could only keep access to the single market by accepting the free movement of all European Union citizens into Britain.

Verhofstadt was appointed last week as the EP's negotiator, and joins the EU Commission's Michel Barnier, and the Council's Didier Seeuws, who are the point men for the Brexit talks.

British prime minister Theresa May has said she will not trigger Article 50 until early 2017 at the earliest.

On the EU's part, the negotiations will be led by the member states, despite the EU Commission's efforts to play the main role in the talks.