Scottish Government figures show that 1,169 of the 3,076 post-probation teachers (38 per cent) went into permanent, full-time positions in state schools last year.
It is a drop of 10 percentage points from 2018-19 and the lowest proportion for at least seven years, according to official figures.
With 42 per cent of teachers going into temporary, full-time posts after their probation year, it is the first time on record that more people have taken temporary jobs rather than permanent ones.
School statistics show that the overall number of teachers rose by 1,153 from 2019, with increases of those teaching in primary, secondary and special needs schools.
But Mr Rennie called for the Government to “stop the temporary funding that leads to temporary jobs”.
The former Scottish Lib Dem leader previously set up a petition that attracted more than 1,400 signatures calling for the Scottish Government to find employment for thousands of teachers facing an uncertain future.
Mr Rennie said: “These figures show that the plummeting number of full-time jobs available for new teachers is part of a far deeper problem with Scottish Government policy, rather than short-term issues created by Covid.
“This casualisation of the teaching workforce must end. We need to stop the temporary funding that leads to temporary jobs.
“The way the Scottish Government has treated thousands of newly qualified teachers has been disgraceful.
“Despite endless election promises, many teachers and their families have been left in a dire position because of incompetent planning by ministers.
“The Scottish Government has finally listened to our pleas with a decision to baseline some funding for future years which will make the funding permanent.
“This teachers’ victory should not have taken weeks of bad press for ministers to recognise the problems facing our education system.
“But the SNP Government must go further by making more of the funding permanent so that it can be used to issue more permanent contracts.”
A Scottish Government spokeswoman said that the government had provided additional investment to support the recruitment of extra educational staff in Scotland throughout the pandemic.
She said: “While local authorities are responsible for the recruitment of their staff, we have taken action to support councils to recruit permanent teachers.
“Since the start of the pandemic, we have provided £240 million of additional investment, over two financial years, for the recruitment of additional education staff.
“This has supported the recruitment of over 2,200 additional teachers and over 500 support staff in the 2020-21 school year.
“In August, we announced that further additional permanent funding equating to £145.5 million per annum will be baselined in to the local government settlement from April 2022.
“This will ensure sustained employment of additional teachers while meeting local needs and benefitting Scotland’s children and young people.
“We will continue to do everything we can to maximise the number of jobs available for teachers, including permanent posts.”