The UK and European Union are set to begin post-Brexit trade talks next week, after EU ministers approved their negotiating mandate.
A 46-page document was approved by the EU General Affairs Councilon Tuesday and will be the basis for negotiations, which are set to be led by Michel Barnier.
Speaking at a press conference, Mr Barnier outlined a number of red lines, including on fishing and regulatory standards, which he said the UK needs to adhere to in order to secure any future agreement.
Mr Barnier said there needs to be a continutation of the existing fishing rights "or there won't be any agreement at all".
He added: "There will be no ambiguity at all around that.
"The trade agreement will be associated with a fisheries agreement and an agreement about a level playing field or there won't be any agreement at all."
Mr Barnier said the negotiations would be "complex, demanding and difficult".
He added: "We have very little time ahead of us. We will use it as effectively, as intelligently, as possible... Let's get this negotiation done and off to a good start.
The EU said it wants to secure a free trade agreement with the UK, but this would require the UK to agree to "cooperation on customs and regulatory aspects", something which the prime minister has previously ruled out.
They also stressed that a future partnership between the UK and EU be "underpinned by robust commitments to ensure a level playing field for open and fair competition, given the EU and the UK's geographic proximity and economic interdependence".
Croatian Europe minister Andreja Metelko-Zgombic said: "The council has adopted a clear and strong mandate for our negotiator, Michel Barnier.
"This confirms our readiness to offer an ambitious, wide-ranging and balanced partnership to the UK for the benefit of both sides.
"The EU is now ready to start negotiations."
Ireland's foreign minister Simon Coveney said the UK that it must honour the Withdrawal Agreement Bill, signed off by both the EU and the UK, as a way of ensuring the Good Friday Agreement remains in tact.
He also said the offer the EU was making to the UK was "generous and fair".
The first round of talks is expected in Brussels on Monday, with a second round in London later in March.
A spokesman for Boris Johnson confirmed the UK's own mandate had been agreed.
They said: "We look forward to engaging with the EU constructively following the publication of their mandate.
"The UK's primary objective in the negotiations is to ensure that we restore our economic and political independence on January 1 2021.
"At the end of this year we will be leaving the single market and customs union and taking back control of our own laws and our own trade."
Downing Street said the Government wants the same treatment as other major economies who have signed trade deals with the EU.
A tweet from the Number 10 press office read: "The EU has respected the autonomy of other major economies around the world such as Canada and Japan when signing trade deals with them. We just want the same.
"We agree the UK's trade with the EU is significant. The US's is on the same scale - yet that did not stop the EU being willing to offer the US zero tariffs without the kind of level playing field commitments or the legal oversight they have put in today's mandate."
British ministers are expected to seek a Canada-style agreement with zero tariffs, a proposal Mr Johnson and his Europe adviser David Frost have set out in speeches in recent weeks.
The tight time schedule for the talks remains an issue, with European ministers voicing concerns over the Prime Minister's unwillingness to extend the deadline beyond December.
Mr Barnier said the bloc would not agree a deal "at any price" and warned that the deadline set by the UK could limit the scope of the agreement.
"In a very brief period, you can't do everything, we will do as much as we can under pressure of time," he said.