Senior Labour MP Yvette Cooper has accused Ms May of not being honest with voters claiming that people "can't believe a word she says".
Speaking in the Commons ahead of a vote to approve her election plan, Ms Cooper said: "The Prime Minister yesterday said she was calling a general election because Parliament was blocking Brexit.
"But three quarters of MPs and two thirds of the Lords voted for Article 50 - so that's not true, is it. A month ago she told her official spokesman to rule out an early general election, and that wasn't true either, was it."
The future Labour leadership contender added: "She wants us to believe she is a woman of her word. Isn't the truth that we cannot believe a single word she says?"
Ms May made her call for an election from Downing Street on Tuesday, saying it was necessary in part because MPs and Lords had attempted to stymie her drive to Brexit.
The call also came after months of clear denials from her and her aides that any election would be called, on the grounds that it would create instability and uncertainty for the country.
Ms Cooper's attack mirrored one made by the Tories on Tony Blair, when Michael Howard repeatedly asked: "Why should people ever believe a word he says again".
Ms May responded: "This House and this Parliament voted to trigger Article 50."
She went on: "I think it is right now to ask the British people to put their trust in me and the Conservative party to deliver on their vote last year a Brexit plan that will make a success for this country and deliver a stronger fairer global Britain in the future."Reuse content