The Prince of Wales has urged governments to attack demand for illegal wildlife products and follow the money to seize the "ill-gotten gains" from organised gangs threatening the annihilation of endangered species.

Addressing heads of state and officials from about 50 countries at a high-level London summit to tackle the threat to animals including tigers, elephants and rhinos, Charles warned the scale of the poaching crisis had reached "unimaginable heights".

Flanked by his sons, the Duke of Cambridge and Prince Harry, he praised the leaders and foreign government ministers for meeting at Lancaster House.

"Today, if I may say so, you are breaking new ground by coming together and committing – at high levels never before seen at a conference on this topic – to take urgent action to put a stop to this trade, which has become a grave threat not only to the wildlife and the people who protect them, but also to the security of nations."

He added: "Next month, I hope it will be possible to convene a meeting to encourage governments, banks, accounting firms, security agencies and others to make greater use of financial tools to tackle organised crime engaged in the illegal wildlife trade.

"As many experts are telling us, if we 'follow the money' and take back organised crime's ill-gotten gains – now done of course to combat trafficking in drugs, weapons and people – we can send a strong message to criminals that there are serious consequences when they kill endangered wildlife for profit."

Charles, a long-term campaigner on wildlife conservation, told the conference: "Today, the government leaders assembled here will sign the London Declaration, committing to several bold new steps forward, including new pledges to address what is the most significant problem in my view – that of demand for and consumption of specific products from critically endangered wildlife.

"Most recently, demand from Asia – particularly China – has fuelled the trade, but we also know that the United States and Europe are contributing to it."

He had been approached by a group of African presidents a year ago who made an "impassioned plea for help", he said.

"Organised gangs, terrorist groups and militia were slaughtering ever greater numbers of elephants for their ivory and rhinoceros for their horns. Most threatened of all, they said, is the elephant – an integral part of the ecological and social fabric of the African continent and a keystone species.

"Their slaughter in both forests and savannahs had created frighteningly silent and sterile places. And without the elephants, some of whose populations are no longer viable and yet are often irreplaceable agents in seed germination, the long-term ecology or many forests is fatally disrupted. No elephants, no forests."

"This tragedy, of course, is not confined to Africa alone. It is crucial to understand that Asia's, specifically India's, wildlife is also being decimated and if the world's focus remains solely on Africa we risk losing south-east Asia's wildlife, which includes 20% of the world's species."

He added: "As vital as strong enforcement is, we can – indeed we must – attack demand."

It had been done before, successfully, he said, citing a campaign against shark fin soup. The result was "80-85% of those in major cities in China had reduced consumption – or completely stopped consuming – shark fin soup".

He continued: "There is not a moment to lose if we are to save the species whose loss will not only diminish us all, but also expose their abandoned habitat to ever greater risk of destruction, with dire consequences for humanity."

On Wednesday, Prince William launched a new organisation, United for Wildlife, to help combat the trade, and said in a video message: "We have to be the generation that stopped the illegal wildlife trade, and secured the future of these magnificent animals, and their habitats, for if we fail, it will be too late." However, he came under fire from some environmentalists for shooting wild boar in Spain just days before the summit.

William, David Beckham and basketball star Yao Ming have released a video message urging people around the world not to support the trade in rhino horn.

The trio are filmed walking on the pitch at Wembley stadium in London surrounded by computer-generated rhinos.

The WildAid campaign video tells viewers that the world's entire rhino population could fit inside the stadium, but their numbers could be increased by stopping the demand for rhino horn.

In the message, William says: "Together we can save our wild rhinos. When the buying stops, the killing can too."

Beckham adds: "Ask your friends and family never to buy rhino horn."

In a separate video, actor Jackie Chan warns viewers that buying rhino horn supports the dark side of the trade.

"You're paying for guns, bullets, poisoned arrows, chainsaws, axes, and machetes to hack off the face of the rhino. And you are paying for the life of a beautiful creature," he says.

The prime minister, David Cameron, was due to speak at the conference but his attendance was cut short so he could focus on the flooding in southern England.

In a short address the foreign secretary, William Hague, outlined the steps the conference would agree to take to tackle the "unprecedented crisis".

He said there was "some evidence to show how insurgent or terrorist groups can benefit from the trade" in endangered species, but the conference would result in a "powerful declaration that will demonstrate to the world that we will not tolerate this abhorrent trade".

The governments present would commit themselves to "renounce the use of any products from species threatened with extinction". They would also support the ban on the trade in elephant ivory until the survival of animals in the wild was no longer threatened by poaching.

Hague added the countries represented would "commit ourselves to treat poaching and trafficking as a serious, organised crime in the same category as drugs, arms or people trafficking".

"Poachers think they can act with impunity. We will show them they are wrong.

"There should be no weak link, we will all seek out those who commit these atrocious acts and use the full force of our national and international laws to break these criminal empires."