Nicola Sturgeon has accused the Scottish Conservative leader Ruth Davidson of having "lost the plot" after angry exchanges during First Minister's Questions.

The SNP leader and Davidson sparred at the weekly session in Holyrood over a shortfall in the number of teachers needed in Scotland.

Davidson raised the case of Trinity Academy in Edinburgh which has had to appeal to parents to find a maths teacher because they do not have enough to cover all classes.

The Conservative leader then brought up an email she had received from a teacher trained in England who wanted to teach in Scotland but would have to go through a one-year retraining programme instead of entering straight into the profession.

"That is a qualified maths teacher not allowed to teach maths in Scotland," explained Davidson.

"And he is not alone. We have a crippling shortage of teachers but according to evidence presented to this Parliament this year we have more than 550 qualified teachers from outside Scotland applying to teach here but who have been told by this government to go back to school themselves."

Sturgeon told MSPs that she too had received the same email.

She said: "The circumstances narrated in that email relate back to 2012, since then - and this is the bit I would have thought Ruth Davidson, if she was going to raise this today, might have actually have been aware of - because since then the General Teaching Council for Scotland has introduced provisional conditional registration, which allows teachers qualified outside Scotland to become registered and to take up a teaching post in Scotland while they work towards meeting the minimum requirement."

The First Minister added: "Ruth Davidson asks me why haven't we fixed that. Well I'm afraid Ms Davidson the answer is we have, you just didn't bother to do the research to find out."

Davidson retorted that the change raised by the First Minister had not been fully implemented yet and it was a "smoke and mirrors" tactic deployed to hide her government's record in education.

The fiery exchanges ended with the First Minister telling MSPs: "You always know when Ruth Davidson has lost the plot at First Minister's Questions because we just get the angry waffling in place of a question."