Jeremy Corbyn has denied he will be "toast" if Labour fails to hold on in two crucial by-elections triggered by the resignations of outspoken critics of his leadership.
The party is expected to face a strong challenge from Ukip in Stoke-on-Trent Central, where Tristram Hunt is standing down to become the director of the Victoria and Albert Museum.
And the Conservatives are being tipped to unseat Labour in Copeland where Jamie Reed has quit to take up a position at the Sellafield nuclear power plant.
But despite Labour continuing to trail the Tories in the opinion polls, Mr Corbyn insisted the contests represented an "opportunity" for the party rather than a problem.
Asked on BBC1's The Andrew Marr Show if he would be "toast" if they lost, he replied: "No. Our party is going to fight very hard in those elections.
"You are making the assumption that everything is a problem. It is an opportunity. It is an opportunity to challenge the Government on the NHS, it is an opportunity to challenge them on the chaos of Brexit."
Mr Corbyn also brushed off an opinion poll which showed the Conservatives and Theresa May were now more trusted on the NHS than Labour under his leadership - despite the current winter crisis.
The ComRes poll for the Sunday Mirror and the Independent found 43% thought the Tories would make the better job of managing the NHS this winter compared to 31% who thought Labour would.
Mr Corbyn said: "I think the more people see the reality of the underfunding of the NHS, the reality of the hiving off and privatising of services, the outsourcing of NHS facilities, the more and more disappointed and angry they are going to get. They will understand the case that we are making."
The Labour leader also indicated his support for new curbs on the press and on media ownership.
"I don't think the media are very fair in many ways, particularly towards the Labour Party," he said.
"I think we need a process where there is a right of reply. I think we also need to remove the levels of concentration of ownership in certain organisations. I think (Rupert) Murdoch taking over completely Sky for example is a problem," he said.
He said he hoped the Labour mainifesto for the next general election, due in 2020, would include a commitment to scrap the House of Lords and replace it with an elected second chamber.
"We have a House of Lords which is dominated by a small number of people from London and the south east," he said.
"I would want to see an elected second chamber that is representative of all regions and nations of the United Kingdom. I think that is very, very important. I would like us to get to that position by 2020."