The SNP will announce an independence referendum “within days” if they win in seats being fought by the Liberal Democrats, Jo Swinson claims.
The Lib Dem leader will speak at a rally in Edinburgh a week ahead of polling day.
Party colleagues Willie Rennie, Alex Cole-Hamilton, Christine Jardine and Beatrice Wishart will also speak at the event.
Ms Swinson will tell the audience Nicola Sturgeon should “spend a little less time banging on about independence and a little more time on sorting out our hospitals and mental health services”.
She is expected to say: “For the last three and a half years, the SNP have had front row seats watching the Conservatives fail to get Brexit done.
“They’ve seen that breaking up is hard to do but instead of learning the lessons, the SNP want to repeat the mistakes.
“They’ve watched how hard it is to break up a union of 40 years and they still want to try to break up one of more than 300 years.
“And if the SNP win in the seats we are fighting, they will announce an independence referendum within days. That is not in Scotland’s best interest.”
Meanwhile,Ms Sturgeon will start a national campaign bus tour as she warns there is “seven days to escape Brexit”.
Speaking before the start of the final week tour, she said Boris Johnson “must be stopped next Thursday or it will be open season on Scotland as the Tories start to impose their hard-line Brexit scheme”.
She added: “Together we can stop Brexit. In every seat that the Tories hold in Scotland, the SNP are the main challengers.
“No other party can defeat them in Scotland so to stop Boris Johnson I urge voters to unite around the SNP.
“We have seven days to escape Brexit, lock Boris Johnson out of office and put Scotland’s future in Scotland’s hands.”
Scottish Conservative leader Jackson Carlaw will campaign at the Tunnock’s factory in Uddingston, with a warning that businesses want certainty not further division.
Speaking ahead of the visit, he said: “This typically bogus claim by Nicola Sturgeon is nothing more than a cynical ploy to justify support for her unwanted indyref2 obsession.
“There is one week left to vote Scottish Conservative & Unionist. Stop Sturgeon in her tracks, tell her again – No to indyref2.”