Gordon Brown dismissed claims that he accused Tony Blair of ruining his life as "completely wrong".
The claim is the latest story to emerge from a book by political commentator Andrew Rawnsley, who has also alleged that the Prime Minister was given a "pep talk" by the head of the civil service about his behaviour towards staff.
An excerpt from the book, published in The Guardian, describes a stormy private meeting on the eve of Mr Blair's announcement in 2006 that he would stand down as Prime Minister within a year.
It asserts that Mr Brown demanded that Mr Blair ensure he faced no rival for the Labour leadership succession.
The book, The End of the Party, quotes Mr Blair later telling friends: "He kept shouting at me that I'd ruined his life."
During a visit to Allied Vehicles Ltd in Glasgow today, Mr Brown was asked how damaging the story - and claims that he ordered aides to undermine Chancellor Alistair Darling - was for him in the run-up to a general election.
He responded: "Given that they are both completely wrong, and that you can almost laugh them off, they are so ridiculous.
"I think what people are looking for is someone who gets on with the job. I'm passionate to do things, I want to get things done and I'm very passionate about the future of our country.
"For me, being in the job I am in is about delivering for the people of our country and delivering every day."
The Prime Minister recently admitted that he and Mr Blair had done a deal over the Labour leadership when it came up in 1994. Mr Brown indicated he felt he should have taken over at that point. Instead, he stood aside for Mr Blair on the basis that he would later back Mr Brown to take over in the top job. That did not happen for 13 years.