"I want to record my deep-seated concern and, I believe, the deep-seated concern of many, not just in Scotland but across the United Kingdom right now, at the prospect of some sort of grubby deal between the Tories and the DUP to allow Theresa May to cling to office", she said.
May is holding talks Thursday with other Northern Ireland political parties amid warnings the expected DUP deal will undermine the peace process.
She hosted DUP leader Arlene Foster at Downing Street to thrash out the terms of the Northern Ireland party's backing and agreement to vote with the Tories on policies in the House of Commons to get bills through.
Brexit negotiations had been due to start next Monday, but that timetable has been thrown into doubt by May's disastrous loss of a parliamentary majority last Thursday.
When the Prime Minister sat down for dinner with Emmanuel Macron in Paris Tuesday evening, the new French President - who has set out his stall as an European Union reformer - likely reminded her that the clock is ticking.
Britain's typically right-wing press savaged May over the election outcome, questioning whether she will be able to remain in power after a result that leaves her reliant on uniting rival factions within her party to deliver Brexit. "I think everyone in the Labour Party and everyone who supported the Labour Party yesterday - young people, old people, everyone in between - I think they should be very proud of what we achieved yesterday".
Ministers have already said that the Queen of England's speech may have to be set back from its scheduled date of next Monday June 19, because of the ongoing negotiations.
Yesterday, May had faced the tough 1922 Committee of her party's backbench MPs amid a brewing rebellion within the ranks after her gamble to call a snap general election backfired, leaving the Tories eight seats short of a majority.
The DUP is believed to be more favorable to a "soft Brexit" that would keep Northern Ireland's border with the Republic of Ireland free-flowing.
Former Prime Minister John Major said he was concerned May's plan to govern with the support of the DUP could pitch the province back into turmoil by persuading "hard men" on both sides of the divide to return to violence.
"Obviously until we have that we can't agree the final details of the Queen's Speech", said May's deputy Damian Green, referring to an agreement with the DUP.
The Orange Lodge of Portadown, a fraternal order of anti-Catholics that counts among its members David Simpson, one of the DUP's 10 members of Parliament, issued a statement over the weekend calling on the party to use its leverage with the prime minister to get her to permit its annual parade to once again pass through Catholic areas. "I can't negotiate with myself", he told European newspapers including the Financial Times.
Environment Secretary Michael Gove declined to deny the reports when pressed, but told Sky News that the reality of the election result meant that May and her government would need to reach beyond party lines. "The current uncertainty can not continue". Divisions over Europe helped sink the premierships of Margaret Thatcher, Major and Cameron, and many of her lawmakers and party membership support a sharp break with the EU.
It could also be the place for May "to change her position on Brexit", he added.