A former Tory Welsh secretary who backed Remain said the way EU leaders "sought to belittle" Theresa May in Salzburg made him more keen on Brexit.
Stephen Crabb said he was "taken by surprise" at the way they dismissed her Chequers plan for future relations.
He said their manner "pushes people like me ... more into a position where we say the quicker we're out of this circus, the better".
The Preseli Pembrokeshire MP said Mrs May should "stick to her guns".
Two Cabinet ministers - Boris Johnson and David Davis - resigned over the plan agreed at the prime minister's country residence in July, claiming it would keep the UK tied too closely to EU rules and regulations.
At a summit in Austria on Thursday, EU leaders told Mrs May her proposals for a future economic relationship were unworkable, claiming they would undermine the single market.
Mr Crabb told BBC Radio 4's Today programme the EU's attitude was pushing him into the arms of hard Brexit rebels in the European Research Group (ERG) led by Jacob Rees-Mogg.
"I actually think the Chequers proposal is not perfect but broadly represents the kind of compromising package that protects Britain's industrial base, that protects agriculture and represents a positive position to take into the negotiations," he said.
"The trouble with the position the EU took yesterday is it pushes people like me further into the camp of those who say 'look, we told you so, there is no compromise or flexibility to be found on the EU side'.
The former work and pensions secretary said people like him who sought compromise were left "having more sympathy for the kind of language they [the ERG] have been speaking".
"You've got to engage your brain at this point," Mr Crabb added.
"My gut feeling might have been saying to me yesterday 'look, the quicker we're out of this the better, this negotiation isn't worth the candle'.
"But we've got to stick with it."