Ruth Davidson, the leader of the Scottish Conservatives, is understood to be on the verge of making an announcement about her position, according to reports.
The BBC reported that the MSP is said to be “considering her position”.
The leader, who voted Remain, has been outspoken on the economic impacts of Brexit, and in particular a no-deal Brexit.
Last month Davidson wrote: “When I was debating against the pro-Brexit side in 2016, I don’t remember anybody saying we should crash out of the EU with no arrangements in place to help maintain the vital trade that flows uninterrupted between Britain and the European Union.
“I don’t think the government should pursue a no-deal Brexit and, if it comes to it, I won’t support it.”
She did not support Boris Johnson for leader, favouring first Sajid Javid and then Jeremy Hunt, and is said to have repeated her remarks in a meeting with Johnson after he became prime minister.
Davidson first clashed with the prime minister when she campaigned for Remain in the 2016 European referendum – going up against the Brexiteer in a televised debate at Wembley.
She and partner Jen Wilson welcomed a son, Finn, in October 2018 after Davidson underwent IVF treatment.
A Scottish Tory source told the Mirror: “She has given a lot to the party, and in return, when she pulling a double shift as a new mum, she’s been ignored on key issues by team Boris.”
Reports of her possible departure shocked fellow politicians in Scotland.
Scottish Labour leader Richard Leonard said the loss of Davidson would be a “real blow to her party”.
The Labour MSP added: “This shows that even within his own ranks, Boris Johnson is already losing support and credibility.”
Scottish Liberal Democrat leader Willie Rennie said: “It’s no surprise Ruth Davidson has run out of reasons to stand by this dangerous and power hungr prime minister.
“There must be lots of other like-minded Conservatives who are horrified at this blatant abuse of power and can’t stomach being party to this destructive agenda any longer. They should take this as the signal to abandon ship.”
Ian Murray, the Labour MP for Edinburgh South, said: “Ruth Davidson is a formidable politician and her departure will be deeply felt by her party.
“She campaigned tirelessly for a Remain vote in the EU referendum, but the Tories under Boris Johnson have become a hard Brexit party, so it is not surprising that it has come to this.”
Pamela Nash, chief executive of the campaign group Scotland in Union, said: “Ruth’s leadership will be remembered for her relentless work making the case for Scotland to remain in the UK.
“Her departure as leader would be sad news for Scotland, which needs vocal champions to stand against the SNP’s divisive nationalism.”
A spokesman for the Scottish Conservatives similarly said: “Ruth will make her position clear in due course. There will be no further comment tonight.”