Prince William launched an ambitious five-year project which seeks to end homelessness in Britain on Monday, saying it was a "big task".

William, 41, the eldest son of King Charles and the heir to the throne, has long been a supporter of charities working with the homeless, inspired by his late mother Princess Diana, who took him to visit a shelter when he was 11.

He slept rough on a winter's night in 2009 to highlight the issue and last year was spotted on the streets of London selling copies of the "Big Issue" magazine, a title that is normally sold by the homeless.

His new "Homewards" programme, backed by 3 million pounds from his charitable foundation, will provide funding, expertise and partnerships to help prevent homelessness in six areas.

The prince will tour the country on Monday and Tuesday to publicise the project and meet those involved in tackling the issue.

"I am fortunate to have seen first-hand the tireless work of people and organisations across the sector, the tangible impact their efforts can have and what can be done when communities are able to focus on preventing homelessness, rather than managing it," he said in a statement.

"It's a big task, but I firmly believe that by working together it is possible to make homelessness rare, brief, and unrepeated."

The project is backed by the Royal Foundation, the charitable organisation of William and his wife Kate. Each location involved will receive 500,000 pounds ($636,000).

According to the Foundation, more than 300,000 people, half of whom are children, are either sleeping rough or in cars, living in temporary accommodation, hostels or with relatives. Charities have warned that those numbers are expected to rise due to the ongoing cost of living crisis.

The programme, described as "a massive moment for the prince", by his spokesperson, is William's most significant project since he became Prince of Wales following the death of his grandmother Queen Elizabeth last September.

Critics say it was hypocritical for someone with William's wealth to be talking about battling homelessness.

"The last thing we need is for William to get involved in this issue, a man who has three huge homes and a vast estate gifted to him by the state," Graham Smith, chief executive of the anti-monarchy group Republic.

"It is crass and hypocritical of William to get involved in this issue."