READING, England — Graham Smith has plans for the queen’s Platinum Jubilee weekend, but they do not include enjoying the festivities or attending a neighborhood street party.
Instead, Mr. Smith will be hosting an international anti-monarchy conference, and explaining why he thinks Britain should get rid of its royals.
The group he runs, Republic, has spent 40,000 pounds (about $50,400), raised by supporters, to post billboards in cities around the country, urging Britons to “make Elizabeth the last” monarch. He is also marking the event by selling merchandise like coffee mugs and T-shirts with anti-royal slogans.
Queen Elizabeth’s big anniversary of seven decades on the throne is nothing much to celebrate, thinks Mr. Smith, who was born and raised in Bristol, in the west of England, and then spent several years in Australia before returning home.
“I certainly don’t view her with any kind of admiration,” he said, drinking a coffee in the town of Reading, west of London, where he now lives. “There is no achievement in what she’s done.”
“Some people would be horrified that someone might say that,” he said. “But it’s not a criticism, it’s an observation: She was given the job for life when she was 25, and she’s still alive 70 years later so she’s still got the job.”
That might seem a minority view in a country embarking on days of pomp and ceremony, where opinion polls show that about six out of 10 people support keeping the royal family; where Queen Elizabeth is widely respected; and where there is relentless, if not universally uncritical, coverage of the monarchy by broadcasters and newspapers.
But support for the royal family has declined in the past few decades and is weakest among young people. So Mr. Smith thinks time is on his side.
Republic, founded in 1983, has about 5,000 subscribing members, plus 100,000 registered supporters.
Since a brief 17th-century experiment with regicide and republicanism ended with the restoration of the royal family, the British monarchy has survived periods of unpopularity. Its role has evolved over the centuries; the queen is head of state and does her best to stay out of politics.
She remains a symbol of national unity at a time when the United Kingdom is under growing threat of breaking up and there is no consensus on what sort of system could replace the monarchy — an institution that even most left-of-center politicians want to keep.
But much of the reverence for the royal family is invested in Queen Elizabeth, giving republicans hope that when her reign ends and the throne passes to Prince Charles, things might change.
“The monarchy’s support is dropping on her watch,” Mr. Smith said. “If she’s not able to stop that happening, then Charles certainly won’t when he’s king.”
Part of this, Mr. Smith thinks, is about changing social attitudes as exemplified by the legalization of same-sex marriage, the growing discussion over issues like mental health, and debates over the #MeToo movement, Black Lives Matter and the legacy of slavery.
In the midst of these changes, the royal family seems an unrepresentative symbol of modern Britain, raising questions about why the country’s next three heads of state are destined to be white men from the most privileged of backgrounds, Mr. Smith thinks.
They also damage Britain, he said, by suggesting “that if you speak with a posh voice, you probably know what you’re doing, you seem to be the right fit for being in charge.”
But perhaps the biggest risk for the royal family is a growing indifference. In an opinion poll commissioned by Republic, a total of 54 percent of respondents said they were “not very” (29 percent) or “not at all” (25 percent) interested in the Platinum Jubilee, with only 11 percent declaring themselves “very interested.”
Although people will turn out to watch the royal ceremonies this week, more might take advantage of the public holiday to go to the beach if the weather is good.
In Reading, where one of Republic’s billboards looks down on a busy street — and where it has survived one attempt to vandalize it — a pro-monarchy resident vented her anger at Mr. Smith.
“I live opposite, and I don’t want to look out of my window and see something that is offensive,” said Rosamund Moon, a retired special-needs teacher. “Everyone is entitled to their opinions, but it’s pathetic. I support the queen and what she’s done for this country.”
Walking past the billboard later, however, Vince Jones said he was not particularly interested in the jubilee and would not be taking part in the celebrations.
“I don’t see why there should be a royal family today — I don’t see the need for them,” said Mr. Jones, also a retiree, adding, “The current monarch is probably as good as you are going to get, but I’m not looking forward to the next one.”