Nigel Farage hit out at "malicious speculation" that he was in ill health and accused rival party leaders of boring Britain ahead of the general election.
The Ukip leader was the recipient of raucous applause when he took to the podium at the party's spring conference in Margate, Kent.
Farage took to the purple-laden stage after returning to the UK just hours after a speech at the Conservative Political Action Conference (CPAS) in the US.
The Eurosceptic spoke alongside the likes of Republican firebrand Sarah Palin at the right-wing event.
"There's been some considerable speculation as to my whereabouts. But I'm not playing quite the same game as the other party leaders, who I have to say I think are beginning to bore the great British public to death," Farage said.
"There's been a lot of speculation about where I've been, why I haven't been seen on the TV all of the time. My absence from the Westminster scene has even lead our opponents to spread some really quite malicious speculation about my health.
"It's said that I'm seriously Ill and that's why I've not been seen. I'm sorry to disappoint my opponents and I want to make it clear that rumours of my demise have been greatly exaggerated."
Campaigning hard and boosted by polls
Farage told Ukip delegates that he had been campaigning hard in Thanet, where he is standing for election in May.
The Eurosceptic leader also seemed to be boosted after a poll from Survation, which questioned more than 1,000 people, put him ahead of Labour and the Tories in the Kent constituency.
Farage went on to attack the coalition government's record on defence spending. He argued some money from the UK's foreign aid budget should be given to the Ministry of Defence (MoD) in a bid to boost the armed forces.
"It beggars belief that Cameron says his proudest achievement is ensuring we spend more on aid proportionately than any other country in the world. Let's spend some of that money on defence," Farage said.
The Ukip leader also attack David Cameron over his failure to meet his net migration target to the UK of "thousands" after the Office for National Statistics (ONS) revealed numbers had soared to almost 300,000.
The speech comes with less than 70 days to go until the general election, with Ukip polling around 15% in national surveys.