Theresa May will tell her fellow European Union leaders that the Brexit vote must be honored and there will be no second referendum as a way to stop the U.K. leaving the bloc. 

Arriving at her first EU summit on Thursday, the prime minister said Britain is on a one-way track out of the EU after some leaders suggested Brexit might not happen.
 
“I’m here with a very clear message, the U.K.’s leaving the EU,” May told reporters in Brussels. “But we will continue to play a full role until we do and will be a strong and dependable partner after we leave.”

May’s comments to her fellow leaders, which she is planning to deliver during a working dinner during the two-day summit, will be her clearest signal yet that she isn’t seeking a close relationship between the U.K. and the EU after Brexit, a British official said. 

While German Chancellor Angela Merkel is among those who have said the bloc must face reality on Brexit, the starkness of May’s message will quash any lingering hopes of a reversal and risks fanning speculation that the government wants a clean break from the single market.

EU President Donald Tusk said last week that Britain could ultimately decide to stay in the EU because the 28-nation bloc wouldn’t offer May any alternative deal to a so-called “hard Brexit,” which would probably mean the loss of tariff-free trading rights.

David Fuller's view

Theresa May will have to be very candid.  She is sensibly doing this by telling the EU that the Referendum decision was final.  The follow-up should be that the UK will be leaving the EU without delay.  This is crucial because she will be at a disadvantage if trying to negotiate within the farrago of the EU’s delaying tactics, so obviously intended to prevent countries from leaving. 

Conversely, she will have the upper hand in negotiations once the UK is out of the EU.  Everyone knows that the EU will be weaker if it does not have close ties with an independent UK.