Ian Blackford has likened Boris Johnson to a "dead parrot" in a reference to Monty Python during Prime Minister's Questions (PMQs).
The SNP Westminster leader criticised the Prime Minister after a series of resignations from his Government put new pressure on his position.
Mr Blackford said it was a "minor miracle" that Boris Johnson was in a position to answer questions during the PMQs session.
He told the Commons: "It's often said that a week is a long time in politics but it turns out 10 days is truly a lifetime.
"Let's face it, it's a minor miracle that the Prime Minister has even made it through to Prime Minister's Questions and he really ought to see the faces behind him, because it really is over.
"A few weeks ago I compared the Prime Minister to Monty Python's Black Knight, turns out I was wrong, he's actually the dead parrot.
"I hope the dishonesty of his leadership follows him out of the Downing Street door."
Earlier today, Mr Blackford said Mr Johnson needs to “realise this is over” and quit.
With the Tory leader struggling to cling to power in Downing Street following a dramatic series of resignations, Mr Blackford said Mr Johnson has lost the trust of both voters and his party and should step aside to allow Westminster to focus on the “immense challenges” facing the country.
But he appeared to rule out using any snap general election as a “de-facto referendum” on Scottish independence, saying this would go against the plan outlined by First Minister Nicola Sturgeon.
The “sequence of that” involves going to the Supreme Court first, Mr Blackford said, with judges having been asked to rule whether the Scottish Government can organise its own consultative ballot without UK consent.
If Supreme Court judges rule against the Scottish Government, Mr Blackford said “we will look at our tactics for an independence referendum using a general election”.
A row over Boris Johnson's knowledge of sexual misconduct allegations facing Chris Pincher has erupted. UK Parliament
Mr Blackford was speaking after Will Quince resigned as Mr Johnson’s children and families minister on Wednesday, and Laura Trott quit as a ministerial aide. She said trust in politics “has been lost”.
Ian Blackford is a vocal critic of the PM. Image: Parliament
Their resignations followed a string of departures from Mr Johnson’s Government on Tuesday evening, led by chancellor Rishi Sunak and health secretary Sajid Javid.
In the wake of Mr Blackford’s comments, justice minister Victoria Atkins, Treasury minister John Glen and schools minister Robin Walker also resigned, while Tory MPs publicly revoked their support for the Prime Minister.
Scottish Conservative leader Douglas Ross also made clear he has no confidence in Mr Johnson.
A party spokesman said: “Douglas made his position clear in the vote of no confidence against Boris Johnson. That remains his position.”
Lord Duncan said if the Tories can install a new leader in Number 10, the party could still do “good things”.
He said: “At the moment much of the concern is about an individual. If a new individual can come in, shake that up, with such a significant majority good things can still be done by this party in government.”
Ian Blackford feels the number of resignations has reached 'crisis point' for the Prime Minister. Image: PA
Boris Johnson's position is in question after Rishi Sunak and Sajid Javid's resignations. Justin Tallis