Some of Labour's seats in Wales will be "very vulnerable" in a snap general election, a Plaid Cymru Liz Saville Roberts has said.
She spoke before MPs voted in favour of triggering the 8 June general election.
But Labour shadow defence secretary Nia Griffith said her party was ready for the fight.
Welsh Secretary Alun Cairns said calling the election was the right decision for the country's security and stability.
A total of 522 MPs from all parties voted to allow an early general election to take place - with Cynon Valley's Ann Clwyd the only Welsh MP among the 13 to vote against.
"I voted against calling an early general election because this is a cynical distraction from Brexit," she said on Twitter.
Eight Welsh Labour MPs - Geraint Davies, Paul Flynn, Madeleine Moon, Wayne David, Jo Stevens, Susan Elan Jones, David Hanson and Chris Bryant - did not take part in the vote.
It came after Mrs May made a shock announcement to call for the early election a day earlier.
Ms Saville Roberts, MP for Dwyfor Meirionnydd, speculated on BBC Radio Wales that Welsh Labour would do its "level best" to present itself as being led by Welsh First Minister Carwyn Jones.
"But Welsh people know that Labour are led by Jeremy Corbyn," said the Plaid MP, whose party is defending three seats in Wales.
Speaking on the Good Morning Wales programme, she claimed some Labour stalwarts had shown "no thirst for the fight".
"We are going to see some very vulnerable Labour seats in Wales. And we're going to be there chomping at the bit," she added.
Ms Griffith said she welcomed the election as an "opportunity for people to choose".
She said the Labour party had been conscious a snap election could be called "but sadly the prime minister lied to us".
However, she said the party was ready.
She refused to discuss what a bad result could mean for the future of Jeremy Corby as leader of the party, adding: "A good result is that we have the opportunity to lead the country."
Welsh Secretary Alun Cairns said the prime minister had called an election so she could "strengthen her hand" in the Brexit negotiations if the party won a bigger majority.
Mr Cairns said the UK government had a small majority, something EU leaders could "exploit".
He added the election was "clearly a challenge" for the Conservatives and there was a "risk", but he said calling an election was the "right thing to do".
During the debate on the early election Plaid Cymru's Hywel Williams said that the Prime Minister's record was as straight as "the legendary European banana".
He said the election was not about "seeing off" her opponents on the opposite side of the House of Commons, but her enemies behind her.
Neil Hamilton, UKIP group leader, said his party would be the "guard dogs of Brexit", adding: "We don't trust Theresa May to deliver, particularly on immigration control".
He said the voting system for general elections - first past the post - was "very unfair" especially to small parties.
But he added: "We'll use this election as an opportunity to get our message across of Britain for the British."
Meanwhile, former Labour first minister Rhodri Morgan said Jeremy Corbyn should have "nice clear punchy messages" in Labour's general election campaign.
Asked what his election advice to Mr Corbyn would be, Mr Morgan said: "Nice clearly punch messages reflecting the parlous state of the health service, the crazy idea about the restoration of grammar schools [and] the problems over school places in England."
But in Wales, where many public services are devolved, Mr Morgan said there was "no reason for us not to have an election about Brexit".
Lord Mike German, former Welsh Liberal Democrat leader and now treasurer for the UK party, said his party was "the only ones who could stop the hard Brexit of the Tories".
He said voters understood this and, within two hours of Mrs May making her announcement, the party had signed up more than 2,000 new members across the UK.
Theresa May has told the BBC she will not take part in TV debates ahead of the planned election.
Plaid Cymru leader Leanne Wood said Mrs May should be "empty chaired" if she refused to take part.
Analysis by BBC Wales political editor Nick Servini
The question is whether Jeremy Corbyn's current poll ratings act as a counter-balance to what will presumably be a much stronger Labour local campaign than two years ago.
More broadly, I expect Labour to run a highly defensive effort to hold onto what they have got under pressure from all angles.