The Don Valley MP told Robert Peston on his ITV television show this morning that Thursday's General Election was 'unnecessary' and was an attempt by Prime Minister Theresa May to bolster her mandate because she already had backing for her Brexit negotiations.
She said: "The hubris that she has demonstrated has been her downfall.
"Clearly there is less to Theresa than meets the eye."
Ms Flint, who has represented the Don Valley constituency for 20 years, added:
"But this is a nightmare for Theresa May because it certainly isn't what she set out [in] her plans seven weeks ago."
This comes as Mrs May's grip on power appears to be far from secure, as a deal with the Democratic Unionist Party (DUP) is still yet to be finalised.
Talks on the arrangement are set to continue during the week as Mrs May desperately tries to shore up her position after losing her Commons majority in the election.
Ms Flint has previously been a vocal critic of leader Jeremy Corbyn, claiming last year that he was not capable of leading Labour into a General Election.
Mr Peston told Ms Flint this morning: "You were a critic of Jeremy Corbyn. You were wrong weren't you?"
She responded: "I think I did underestimate Jeremy in the campaign, and it's quite clear looking at the results.
"And there's lots of different stories, and they'll be writing books about this forever more, but actually, you know, he did both in terms of his leadership bid but also as the leader of the Labour Party make the point of how you can galvanise young people.
"And there's one thing that's for sure - that certainly did happen. Lots of different reasons for that. I think Jeremy has an appeal there. But I also think there was a great deal of hostility from those young people."
Labour gained 30 seats in Thursday's general election to take its total to 262 seats, but the Conservatives remain the largest party in Parliament with 318 seats.
This is more than the total of Labour, Lib Dems, SNP, Plaid Cymru and Green Party. The number needed for a majority is 326.