Jeremy Corbyn has said speculation about his future as Labour leader is "absurd" so early in the General Election campaign.
Mr Corbyn made the remark after being asked whether he would step down if Labour lost on 8 June.
It follows a YouGov opinion poll which suggested 24% of Britons intended to vote for his party, compared with 48% for the Conservatives.
Mr Corbyn told Sky's Rebecca Williams in Bristol: "Listen - we've just started the election campaign. We're 72 hours into it and I'm loving every moment of it.
"We're gaining support and we're gaining a huge amount of ground. Watch this space.
"We're putting a message out there: this country does not have to be so divided, there does not have to be such appalling levels of poverty and unachieved ambition because of people growing up in poverty. The Labour Party is totally united in putting that message out."
Mr Corbyn used the second day of his election campaign to claim the Conservatives' education policy had left children crammed "like sardines" into "super-sized school classes".
The Labour leader cited Government figures which show that more than 40,000 primary school children in England were taught in classes of 36 or more last year - up from 38,500 in 2015.
During a stump speech at a community centre in Swindon, he told supporters: "We will fund our schools properly. We won't put the priority into grammar schools and selectivity - we will put the priority into all children in all of our schools.
"Class sizes are rising all over the country. It's pretty obvious to me that if you're in a class of 36, you're not going to get a great deal of attention from the teacher compared to if you're in a smaller class of 30 or under."
The Tories replied by saying Mr Corbyn had made a "massive own goal" because class sizes have also been rising in Wales, where Labour is in government.
Labour is also planning to add VAT on private school tuition fees in order to fund free school meals for all primary school children in England.
Sky's Adam Boulton asked shadow schools minister Mike Kane whether such a move would put further pressure on the state school system and worsen class sizes, given the tax hike could price some families out of private education altogether.
After being pushed for a straight answer, Mr Kane insisted that a "fully-costed manifesto" would be brought forward by the Opposition in due course.
Other pledges made by Mr Corbyn on the campaign trail include ending zero-hours contracts, introducing a living wage of £10 an hour, and bringing in legislation to protect and encourage small business.
He also said a Labour government would guarantee the "triple lock" on the state pension, which ensures that they rise by at least 2.5% each year.
Last year, a report by the Commons Work and Pensions Committee warned that the safeguard should be scrapped because it is "inherently unsustainable" and will worsen an economy which is already heavily "skewed" towards baby boomers and against millennials.