Corbyn later ruled out any post-election coalition with the Scottish National Party.
In a preview of her election strategy, Mrs May said: "I will be taking out to the country in this campaign a proud record of a Conservative government".
Meanwhile, Opposition Leader Jeremy Corbyn will kick off his campaign on Thursday by vowing to defeat what he calls a "cosy cartel" at the heart of British politics that protects the interests of the wealthy.
In her first campaign visit, to a Labour marginal in Bolton on Wednesday, the Prime Minister told an invited audience: "There's a very clear choice at this election". A ruling alliance with the Labour Party, however, was dismissed by senior Lib Dems, who hoped to distance themselves from "toxic" Corbyn.
"In a lot of seats, there are a lot of "Remain" voters to appeal to", Ford said, particularly as the main opposition Labour party's official position on leaving the European Union is "deeply unclear".
She wants to take Britain out of the single market and customs union and is counting on an increased majority in parliament to give her greater flexibility in brokering a deal with her EU counterparts.
"The only way is up" for the party, she wrote.
While Labour may be demoralized and divided under Corbyn's leadership, it doesn't look like he is going anywhere fast.
Mr Corbyn will continue: "They say I don't play by the rules - their rules".
In his first speech of the campaign, he will play the anti-establishment card that resonated in the USA and during Britain's Brexit vote a year ago. And a Labour government elected on June 8th won't play by their rules.
Despite polls giving Tories double-digit leads over Labour with just seven weeks to go, Mr Corbyn will say his party can "change the direction of this election" by "putting the interests of the majority first".
However, all polls taken just before the snap election announcement and immediately afterwards predict a landslide victory for the Conservative party. Tories are seen winning 48 per cent of the votes, with Labour trailing with 24 per cent and Liberal Democrats at 12 per cent, according to a YouGov survey of voting intentions reported by The Times.
Pat Glass, Labour's MP in North West Durham, previously said she would step down in 2020. Now that's been brought forward by three years.
"The SNP remains dominant in Scotland and is likely to retain most of its 56 seats".
One prominent Corbyn critic, Middlesbrough MP Tom Blenkinsop, made explicit that his "irreconcilable differences" with Corbyn had forced him to stand down.
"Labour MPs that now have majorities in the single thousands may be looking over their shoulders", McLeod said. Another, John Woodcock, published a video on Facebook saying he plans to stand again, though can't support Corbyn.
Britain's political parties launched into combat mode on Wednesday after Parliament backed the prime minister's call for a snap general election on June 8. In the 1983 vote, it emerged with 209 seats. "It is because of these differences that I feel I can not, in good faith, stand as the Labour candidate for Middlesbrough South and East Cleveland", Blenkinsop said, according to The Daily Telegraph.