Jeremy Corbyn warned "you don’t achieve peace by planning for war” as he spoke to thousands of people in an anti-Trident rally in central London.
The Labour leader was joined by Scottish first minister Nicola Sturgeon and Plaid Cymru leader Leanne Wood for the march through central London on Saturday.
According to the BBC, Corbyn said: "We live in a world where so many things are possible. Where peace is possible in so many places.
"You don't achieve peace by planning for war, grabbing resources and not respecting each other's human rights.
"Today's demonstration is an expression of many people's opinions and views. I'm here because I believe in a nuclear-free Britain and a nuclear-free future."
Sturgeon labelled the nuclear deterrent “immoral” and "impractical", according to the Press Association.
She said: "It is the norm in the world today to be nuclear-free. It is the exception to the rule to possess nuclear weapons, let that ring out loudly and clearly.
"The use of nuclear weapons would bring about human devastation and suffering on an unimaginable scale."
She said the SNP would be making Trident a political issue at forthcoming elections.
Former Green Party leader Caroline Lucas described nuclear weaponry as "a cold war relic".
She said: "To contemplate using nuclear weapons is both illegal and immoral."
Saturday’s march was estimated by stewards to run into "many tens of thousands”.
The Ministry of Defence has estimated acquiring four new submarines to carry the Trident deterrent will cost £31 billion over the course of the 20-year procurement programme, with a further £10 billion set aside to meet any additional unexpected cost increases.