Canadian taxpayers could be on the hook for millions of dollars a year in security expenses if Britain's Prince Harry and his wife Meghan move there, even part time, as they step away from their royal duties, security experts have said.

Larry Busch, an ex-Royal Canadian Mounted Police officer who directed security for US presidents and royals, said the government would likely have a legal obligation to provide security - especially considering the Queen is Canada's head of state.

'I don't believe they can refuse the government of Canada's security,' he said.

Canada would have a legal obligation to pay for security for Harry and Meghan if they move to the country which could end up costing millions per year, experts have warned (pictured, Harry escorted by his security detail in Toronto)

Larry Busch, an ex-Royal Canadian Mounted Police officer, said he doesn't think the royal couple would be able to refuse Canadian security, even if they wanted to (pictured, the Queen inspects Mounties during a visit to Canada in 2010)

Meghan (left, file image) has already flown back to Canada to be with Archie, leaving Harry (together right) to deal with the family fallout of their decision to step down as senior royals

Meanwhile Mike Zimet, whose eponymous New York security firm has protected clients including Bernie Sanders and actors Lin-Manuel Miranda and Alec Baldwin, said the cost could easily run into the millions per year.

'If they want private protection, then a whole machine needs to be built around them,' he said.

The level of security they need would be defined by a threat assessment, said Joe Balz, president of GloProSec Preventative Services, a Toronto-based security company, and an ex-RCMP officer who has worked with the royal family and other heads of state in the past.

'There's always going to be the odd idiot who causes some type of problem,' Balz said, adding that they would be safer in Canada than in the United States, where gun laws are much laxer.

They also would need to worry about kidnapping of their son, Archie, said Zimet, who called that threat a 'major situation, especially when it comes to terrorists. Kidnap a kid, hold them for ransom, what are the parents going to do?'

Prince Harry and Meghan have said gaining financial autonomy is a key goal, but declined to say whether this extends to the cost of security, stating that their security detail is mandated by the British Home Office.

The Duke and Duchess of Sussex stunned Queen Elizabeth and the rest of the royal family this week by saying they plan to spend much of their time in North America.

While the pair have not said where they plan to reside, many observers pointed to Canada as a logical choice.

The couple spent the last six weeks of 2019 in that nation, part of the British Commonwealth of countries that have the queen as their head of state.

Prince Harry and Meghan Markle spent their first Christmas with baby Archie at this £10million waterfront mansion on Vancouver Island, and there is speculation they could make Canada their permanent home overseas

News of a potential move to Canada has split public opinion, with some praising it as a 'fairy-tale' but others accusing the couple of 'divorcing their duty'.

Writing in the Globe and Mail, Anne Donahue hailed the couple's decision to break with royal protocol and forge a new path as 'the stuff of real fairy tales' while describing it as 'the type of change in which everybody wins'.

'They’ve begun to help dismantle an institution that often seems a historical relic. And they’re very publicly choosing to stop putting up with the nonsense, on their own dime and in their own way – a power move,' she said'

'If they get their way, and a happy ending, that will make it even more of a fairy tale.'

But that enthusiasm was not shared by Judith Timson, writing in the Toronto Star, who saw a couple 'selfishly or in desperate self-preservation demanding to have it both ways' by living the life they want while also 'dipping into the royal till'.

She added: 'Why have a royal family at all which is supposed to represent duty as well as privilege if you can walk away just from the bits you don’t like any time at all?'

Perhaps in answer to that question, a poll for Canadian news company Postmedia found a majority of the country would support Harry becoming the next Governor General of Canada - the Queen's representative in the country.

When asked, 60 per cent of the 1,515 they spoke to said they liked the idea.

The poll was conducted on January 6, two days before the couple announced their plan to move away from their senior royal roles.

The Duke and Duchess of Sussex are understood to have left Archie in Canada after their six-week trip and the eight-month-old is being cared for by their nanny and Meghan's best friend, Jessica Mulroney.

Ms Mulroney lives in Toronto but it is not known if she was with them in the £10million waterfront mansion in Vancouver they occupied between Thanksgiving and the new year.

Meghan flew from London to Canada in the hours after the Sussexes shocked the world and quit as senior royals, the Daily Mail revealed last night.

Queen Elizabeth is said to have been kept in the dark about the timing of Harry and Meghan's departure from the UK, and heard about it from television

Harry is said to have been involved in four-way crisis talks with the Queen, Prince Charles (left) and Prince William (right) as they attempt to work out the fine-print of his move

The couple horrified and shocked Harry's family including the 'hurt and furious' Queen, who had begged them to delay announcing their 'nuclear' plans.

Prince Charles and Prince William only got a copy of the statement ten minutes before it went live on their secretly developed website.

Last night Her Majesty held a series of calls involving herself at Sandringham, Charles at his Scottish home Birkhall, William at Kensington Palace and Harry – without Meghan – at Frogmore Cottage.

But as the abdication crisis rumbled on the Duke of Sussex was also plotting to fly out of Britain, it has emerged, although it is not yet confirmed when he intends to join his wife in Canada.

Meghan may stay there for the foreseeable future and Harry will not be apart from his wife and son for long - but he must also be at Buckingham Palace for an engagement next Thursday.