Ken Livingstone has called the election result "the most unstable Parliament since February 1974."
No party won a majority to form a government in the vote on June 8, leaving a hung Parliament.
Theresa May is due to travel to Buckingham Palace to seek permission from a Queen to form a government, which is likely to hinge on a 'confidence and supply' agreement with the Democratic Unionists.
The former Mayor of London - currently suspended from the Labour Party for a series of comments about Jewish people - called this result "unstable" and suggested another election could be just around the corner.
He said: "This is the most unstable Parliament since February 1974 - there was an election within six months of this.
"It wouldn’t take more of a shift to put Labour in with a working majority - this election has put Jeremy firmly in control of the party.
"The embittered Blairites who have been undermining him for the last 18 months have got to come to terms with this and I think they will."