The EU has “nothing to gain” from the disruption a no-deal Brexit would bring to the UK, European Commission president Jean-Claude Juncker has said.
Mr Juncker said the EU had adopted the “necessary contingency measures”, but said only those who seek to undermine the global legal order would benefit from such an exit.
“We are ready for a no-deal Brexit,” he told MEPs.
“But our union has nothing to gain from great disruption in the United Kingdom.
"The only ones who would benefit are those who resent multilateralism and seek to undermine the global legal order.”
And he hinted Brexit could be delayed further as he said British MEPs may be members of the Parliament for more than several months.
Mr Tusk said: “One of the consequences of our decision is that the UK will hold European elections next month.
“We should approach this seriously as UK members of the European Parliament will be there for several months – maybe longer.
“They will be full members of the Parliament with all the rights and obligations. I am speaking about this today because I have strongly opposed the idea that during this further extension the UK should be treated as a second category member state. No, it cannot.
“Therefore I also ask you to reject similar ideas if they were to be voiced in this House.”
He said: “I know that some have expressed fear that the UK might want to disrupt the EU’s functioning during this time but the EU 27 didn’t give in to such fear and scaremongering.
“In fact, since the very beginning of the Brexit process the UK has been a constructive and responsible EU member state and so we have no reason to believe that this should change.”
European Parliament chief Brexit co-ordinator Guy Verhofstadt expressed his fear that Brexit will “poison” the European elections.
Referring to the delay to Brexit, he said: “I fear that it will continue the uncertainty. I fear that it will prolong the indecision. And I fear most of all that it will import the Brexit mess into the European Union.
“And moreover that it will poison the upcoming European election.”
Meanwhile, Brexit Party leader Nigel Farage claimed his party would win a general election if Theresa May and Labour leader Jeremy Corbyn agree to a permanent customs union compromise.
He told the European Parliament: “If that happens, the Brexit Party won’t win the European elections but it will win the general election because the betrayal will be so complete and utter, so I don’t believe it’s going to happen.”
In Westminster, cross-party talks between Labour and the Government are expected to continue on Tuesday at an official level.