The Scottish people would be voting “without the necessary information” to make a “crucial decision”, the prime minister said in a televised statement.
“Just at this point all our energies should be focused on our negotiations with the European Union about our future relationship,” she said.
It would “make it more difficult for us to get be able to the right deal, and the right deal for the UK”, May stated.
We should “be working together, not pulling apart”, she added. “I say to the SNP now is not the time”.
At the start of this week, Nicola Sturgeon, SNP first minister of Scotland, called for a referendum to be held in the autumn of 2018 or spring of the following year.
Leader of the Scottish Conservatives Ruth Davidson has told the Scottish Parliament there is “no clear political or public consent” for a second referendum.
She said her party rejected it and did not believe another referendum should happen when the Scottish people did not know how the “new relationship with the European Union is working”.
“We don’t want it, we don’t need it,” Davidson told MSPs.