David Melding said he worried any UK government failure would become "the fault of Johnnie European foreigner".
With the Tory leadership winner being announced next week, Mr Melding warned against "any approach, that leads to acrimonious relations with the EU".
The next three months could be like "no other period" in our politics, he said.
The UK is due to leave the European Union on 31 October, the second extension to the UK's original 29 March departure date after the withdrawal deal agreed between Theresa May's government and the EU was rejected three times by MPs.
Both Conservative leadership contenders, Boris Johnson or Jeremy Hunt, have not ruled out leaving the European Union without a deal.
Mr Melding told AMs on Wednesday:
"The next three months will be like no other period, potentially, in our political history in the last hundred years in peacetime.
"We have to realise this is not a normal situation, it's taken three years to get to this stage, but what happens next could be very quick and dramatic."Rejecting a no-deal Brexit as an option, the South Wales Central AM described the suggestion Parliament could be suspended to prevent MPs leaving the EU without negotiating an agreement with the bloc as "preposterous"."Another thing which should be ruled out is any situation, any approach, that leads to acrimonious relations with the EU," he said."We're leaving, it's for us to convince them that we're doing it with respect to all the vital considerations and interests that are out there with our partners and with ourselves."And I do fear a very ugly form of nationalism developing, in certain quarters anyway, that suddenly turns any failure on the part of the UK government to somehow be the fault of Johnnie European foreigner, and that needs to be called out."We need positive relations with the EU from day one, [or] how we're ever going to get the sort of trading relationship that we require?" Mr Melding added.
Yesterday I was (understably) fooled by this.
It seems this is a spoof account and there is no Brexit MEP called Jim McCawber, but it easy to see , how i was taken in.
When a No-Deal Brexit leads to the predicted economic catastrophe , then those who sought it will not take responsibility.
They will blame the EU and specifically Germany and Ireland and the xenophobia will go beyond parody.
Don't think it will not work the UK media will also look for scapegoats and those of us who backed Remain , will also become targets and the "ugly form of nationalism , which Brexit has given birth to, will threaten not only our democratic institutions and even our personal freedom.