Insisting he was “absolutely” ready for a general election, the Labour leader also said the party had already selected its candidates in the majority of marginal seats across the UK, and that he would be on the campaign trail over the summer.
His remarks came after the new prime minister stoked speculation of a snap general election in a speech on Saturday, showcasing his domestic policies on social care and tackling regional inequality.
Despite ruling out calling a vote before Brexit, Mr Johnson could be forced into an election if his government ploughs ahead with a no-deal exit.
Senior cabinet ministers have already admitted the numbers are there to topple the government if a motion of no confidence is tabled in the new administration.
Pressed on when he would call a no-confidence motion, he told Sky News’s Sophy Ridge on Sunday: “Parliament goes back in September, and I think it’s at that point we’ll look at the situation there.
“But it’s also up to the prime minister what he decides to do as well because if he’s trying to take us out on a no-deal Brexit at the end of October, we’ll oppose it.
“I guarantee this: we’ll do everything to prevent a no-deal Brexit, we’ll do everything to challenge this government and we’ll do it at a time of our choosing.”
He added that if Mr Johnson were to change his approach, and call a general election himself, the Labour Party would vote with him to dissolve parliament because the “public deserve an election”.
Asked whether his party was prepared, Mr Corbyn said: “Absolutely, I’ve got my summer campaign plan in place, we’ve got most of our candidates selected in all our marginal constituencies.
“We have many other policy announcements, particularly the ones on the Green Industrial Revolution and the Green New Deal that we’re putting forward, and working out more details on health and social care policies.
“But fundamentally it’s about reducing inequality in Britain and about investing in good quality sustainable jobs for the future through the green energy revolution.”
On his own party’s position on Brexit, Mr Corbyn reiterated that his party was supporting a referendum in all circumstances, and said even if Labour is in government a public vote would be held on the UK’s exit from the bloc.
He refused, however, to say whether Labour would back Remain or its own negotiated deal if the party came to power.
“We’ve got to get in office first to negotiate a deal,” he said. “We’ve got to win an election – if we win an election then we’re going to have talks with the European Union. But at the moment, the danger is a no-deal exit on 31 October with all the problems that brings.”
Mr Corbyn was also asked whether he agreed with remarks from a member of his own front bench that ethnic minority members of Mr Johnson’s cabinet had sold their “souls and self-respect” by accepting jobs at the top table.
“They are Conservatives, they believe in conservatism, they’ve been appointed in their party. I’d leave it at that, I want diversity at all levels in our society,” he replied.
Pressed on whether he thought the new Tory leader was racist, the Labour leader added: “Boris Johnson has said some awful comments about black children, about Muslim women and about people within our society and our community which I absolutely condemn.
“I hope he will understand the hurt that he caused with the remarks that he made.”
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies