Scottish Health Secretary Alex Neil is facing joint opposition calls for his dismissal today in a rare motion of no confidence at Holyrood.
The SNP minister is accused of misleading Parliament over his role in controversial changes to mental health services in his own constituency.
The direct challenge comes a week after Labour leader Johann Lamont said Mr Neil misled Parliament over plans to remove acute mental health beds at Monklands Hospital in Airdrie and Shotts in 2012.
The party revealed emails they say shows Mr Neil had intervened in the decision-making process upon becoming Health Secretary, before stepping back and handing responsibility to his deputy, the public health minister, citing concerns over a "conflict of interest".
Labour will be supported by Tories and Lib Dems when MSPs vote on the motion this afternoon.
First Minister Alex Salmond has already offered his full support to the Health Secretary, who denies any wrongdoing.
The SNP's majority at Holyrood means the opposition cannot win the vote.
It is only the third motion of no confidence since the Scottish Parliament was established in 1999.
Labour MSP Neil Findlay, who lodged today's motion, said: "Despite all the evidence to the contrary, Alex Neil and Alex Salmond continue to blindly claim that no wrongdoing has taken place with the health secretary's involvement in mental health services at NHS Lanarkshire.
"Nearly a week after these damning emails were released under Freedom of Information, Alex Neil's explanation as to why he meddled in local services and then claimed he had excused himself from the decision have not been satisfactory.
"Medical experts stated that keeping Monklands wards open would result in a 'less than optimal service' for patients.
"Yet Alex Neil has been unable to provide any clear rationale or evidence for changing the decision, which is contrary to his own health policy of delivering health services in communities wherever possible.
"Now that it has emerged the wards he ordered to save contain asbestos, his position has been made even more difficult.
"His failure to come up with answers to the questions being asked of him mean he is not fit to be running our health service."
Tory MSP John Lamont, who supported the move, said: "There is a simple principle here - it is not acceptable for a minister to come to the chamber and say things that he knows to be untrue.
"In another time, any minister who misled Parliament would be expected to fall on his sword.
"To see the First Minister defend Alex Neil when he's been caught bang to rights, having misled the chamber, is an unedifying spectacle indeed."
Lib Dems will also back Labour, saying the group "takes the matter of lying to parliament extremely seriously".
Pressure began last week when the Labour leader ran through a timeline of events which appeared to show Mr Neil's office sent an email stating his view is to retain mental health services in Wishaw and Monklands.
The order reversed previous health secretary Nicola Sturgeon's policy, made on the advice of medical professionals, Ms Lamont argued.
Mr Salmond said the Labour leader had made herself and her party look ''ridiculous'' by calling four times for Mr Neil's resignation or dismissal.
''Labour's interest in mental health in Lanarkshire isn't anything to do with the patients, it is just an argument to try and get at an SNP minister,'' he said.
A Scottish Government spokesman said last night: ''The Health Secretary has acted entirely appropriately at every single stage of the process regarding mental health service provision across NHS Lanarkshire and all of the key information in this case has already been in the public domain for a very long time. We look forward to using the opportunity tomorrow to once again outline that position.
''That will ensure the Health Secretary can continue to focus on ensuring our NHS - one of Scotland's greatest success stories - goes on delivering high quality care for thousands of people, day in, day out.''
The SNP tabled the only two earlier motions of no confidence.
One questioned the role of Labour MSP Sam Galbraith, who was education minister during a school exams fiasco in 2000. A second motion in February 2001 questioned the role of Labour transport minister Sarah Boyack in awarding trunk roads contracts to private firms.
Both attempts failed when put to the vote.