Labour former prime minister Tony Blair has said Theresa May is on course to win the General Election "if the polls are right".
Liberal Democrat leader Tim Farron said both Mr Corbyn and Mrs May - who has also ruled out head-to-head appearances - were "running scared" of voters.
Asked over the potential of Labour's stance, Mr McFadden added: "I am committed to securing the best possible deal, in terms of trade, security and investment".
Writing Tuesday in one of the leading newspapers in Wales, the Western Mail, May she said the election was an opportunity to give Britain "the strong and stable leadership it needs to see us through Brexit and beyond".
Starmer said that a Labour government would rewrite May's Brexit negotiating strategy and would focus instead on a deal that retained as numerous benefits as possible of the single market and customs union.
It will also draw on its database of 600,000 supporters to support Labour's Mary Creagh, Conservative Neil Carmichael and Green MP Caroline Lucas.
"And we will approach negotiations in a completely different way to a Tory Brexit: negotiating for the many, not the few.
We will on day one unilaterally guarantee the rights of European Union citizens in this country", said shadow Brexit secretary Keir Starmer on Tuesday (April 25), putting Britain's European Union departure at the centre of the election battle.
May shocked the nation last week when she called an early election less than halfway through her government's five-year term.
Speaking to Sky News, he said: 'If the polls are right we know who is going to be Prime Minister on June 9, that's not the issue.
Elsewhere, Labour will make the NHS the focus of their day of campaigning, with shadow health secretary Jonathan Ashworth set to promise to lift the 1% cap on pay rises for "undervalued" health service workers.
She accused rival political parties of seeking to disrupt Britain's Brexit negotiations, "even as 27 other European countries line up to oppose us".
"A vote for any other party would be a vote for a weak and failing Jeremy Corbyn propped up by a coalition of chaos which would risk our national future".
Mrs May said the Conservatives had a "positive message and will fight a positive campaign".
She is backed by more than 60% of votes to do a more capable job than Mr Corbyn, who was supported by only 23%.
The Prime Minister, Theresa May, paid a flying visit to Bridgend on Tuesday (April 25) and the national press were in no doubt that there was one objective - to "park her tanks on Carwyn's lawn".