Dame Joanna Lumley has called for a change in the debate on immigration and said the focus should be on tackling the reasons why people migrate.

The veteran actor and campaigner said a lack of food, infrastructure and warfare is the driver for a lot of world migration.

She said a country like the UK cannot support unlimited migration and more needs to be done to improve stability and opportunities in developing countries.

“I think we have stopped looking at what the problems are when there are these great shifts of people,” Dame Joanna said.

“Most people would much rather remain in their own homeland. We all have a great protection feeling to our own homeland.

Dame Joanna campaigned for the rights of Nepalese soldiers to get full UK residency rights (Stefan Rousseau/PA)

“The reason they move is that either it cannot yield enough food for them to live on, or the warfare is such that they’re in danger of their lives, or they want a better life.

“Rather than everybody coming to where those things do exist, which is largely kind of Europe and places like this.

“How are we in the world going to spread this back again so you can stay in your fabulous country.

“You can grow crops, you can have factories and things like this, you can have schools and hospitals, everything can work here, but it must have been made safe and stable and functioning.

“You don’t get to that stage by putting up fences. You do something else.

“Of course, a tiny country can’t support millions and millions of people, but we’ve got to start thinking outwards a bit more.

“We’ve got to start thinking, how can we go to that country and get fresh water to irrigate their land?

“We’ve got to grow the desert, to green the desert, to plant the trees to stabilise the land.”

Dame Joanna, 79, has been involved in many campaigns over the years, such as the Gurkhas, animal welfare and supporting asylum seekers.

She was born in India while her father was serving with the Gurkhas and spent much of her childhood overseas with her family.

“I’ve still got my British nationality papers because my father had been born in Lahore, and so two of us born abroad. I’ve got them just in case they tried to throw me out,” she joked.

Dame Joanna was speaking in conversation with broadcaster Emma Freud at the Cheltenham Literature Festival to promote her new book, My Book Of Treasures: A Collection Of Favourite Writings, which is comprised of her favourite writings, thoughts and quotes, as written in her private notebooks.

Dame Joanna Lumley got her big acting break playing Purdey in The New Avengers alongside Gareth Hunt, centre, and Patrick MacNee (PA)

She said she had wanted to be an actor since she first performed on stage at school aged six.

“I was an Army brat, as they called them,” she said. “I was born in India, and then went out to Hong Kong, then went to what is now Malaysia with my father’s regiment the Gurkhas.

“I was six. Do you remember that poem of AA Milne The King’s Breakfast?

“I was the Queen, and mummy made me a lovely blue dress, a little gold crown made of cardboard.

“I was to just walk on and say things like, ‘Could we have some butter for the royal slice of bread?’

“It all seemed completely normal and fine, until I got to the wings, just got to the side of the stage.

“I thought my heart was going to explode with terror. I thought I would go deaf and blind, so I walked out of the stage, and I had to say the lines.

“But you know, something happened. I knew then, for sure, that that was what I was going to be doing for the rest of my life.”

After leaving school Dame Joanna was turned down by the Royal Academy of Dramatic Art but got her big break as Purdey in The New Avengers.

“It sounds extraordinary to say now but the hunt for The New Avenger woman was almost as keen as the thought of a new James Bond,” she said.

“Nobody knew who it would be. It was 10 years since the last Avengers.

“Anyway, it was me in the end, so that was my lucky break.

“But I was desperate. Nobody ever thinks that you had sour milk because you couldn’t afford to get new stuff.

“That you had to stamp on sheets in the bath because you couldn’t even afford the launderette. Nobody sees that thing. It’s not sad, it wasn’t boo-hoo sad, it was just poor.”

Dame Joanna also referenced the Bible, saying, “Do not mistreat strangers, for they may be angels in human form,” highlighting the moral imperative to treat migrants with kindness and empathy.