George "Johnny" Johnson was 22 when he took part in the 1943 air raid using experimental bouncing bombs in Germany.
TV presenter Ms Vorderman said it was "absolutely disgraceful" the 95-year-old was omitted from the New Year's Honours list, despite being nominated.
The Cabinet Office said it could not comment on nominations.
An ambassador for the RAF Air Cadets for the past two years, Ms Vorderman launched her petition at the beginning of January.
It follows a petition by campaigner Paul Walmsley who also wanted the recognition for the man who retired as a squadron leader.
A trained pilot, Ms Vorderman first met Mr Johnson last year and said she was "overwhelmed and humbled by his achievements and what he has done for this country".
"The volume of signatures in such a short space of time shows the respect the British public have for Johnny and all who fought with him," she said.
"I can't think of anyone who deserves a knighthood more."
Mr Johnson, from Bristol, is the last surviving member of the Bomber Command crews who used Barnes Wallis's revolutionary bouncing bombs - releasing them 60ft above ground.
The bombs were released on a night of raids on German dams in 1943 in an effort to disable Hitler's industrial heartland.
A petition launched by Carol Vorderman calling for the last surviving Dambuster to be knighted has received 200,000 signatures.