Sorry seems to be the easiest word

Canada's prime minister, Stephen Harper, apologised to Chinese Canadians last week for a punitive tax, first set in 1885, which was designed to keep the Chinese immigrants who helped build the country's railway from settling here and bringing over their families.

He offered what he described as "symbolic" payments of $17,792 (£9,785) to about 20 immigrants who paid what was known as the head tax, which was collected until 1923. Roughly 200 surviving spouses will also get the payment.

But saying sorry for one historic wrong means Mr Harper is facing enormous pressure from other communities seeking redress. Canada is a nation of immigrants, and many of them faced state-sanctioned discrimination at some point in their history in the country.

The Sikh community wants redress for the treatment of passengers on the Komagata Maru, a ship that was denied the right to land in Vancouver in 1914, and sent back to India.

According to the Canadian Council on Race Relations, other groups seeking redress include: leprosy patients, who were mostly Chinese, imprisoned on two islands on the west coast between 1891 and 1956; Black people from the Caribbean, who were treated unjustly between 1900 and 1932; Ukrainian Canadians, interned during the first world war; people of Jewish descent who were denied entry into Canada from 1938 to 1948; Italian Canadians interned during the second world war; German Canadians interned during the second world war; African Canadians and the Doukhobors.

Who will be next? Margaret Wente, a columnist at the Globe and Mail newspaper, argues it should be Americans living in Canada. "As an American Canadian, I believe it is way past time for the government to acknowledge the injustices done to my people," she writes. "American immigrants to Canada are the targets of the grossest sort of suspicion, discrimination, hostility and abuse."

Canadian history, she says, is "increasingly a narrative of oppressors and oppressed".

Canadian prime ministers have all been under pressure to acknowledge historic grievances.

The Japanese Canadians who were interned during the second world war were given an apology and compensation under a former prime minister, Brian Mulroney, a Conservative.

But other prime ministers have been reluctant to open the floodgates. Pierre Trudeau said the apologies would never end in a country like Canada, and that it was more important to focus on building a united and just country.

Jean Chretien took the same approach, but his successor, Paul Martin, was more open to the idea.

Like Mr Harper, who beat him in the general election earlier this year, Mr Martin was anxious not to alienate potential voters.

In general, new immigrants have historically supported the Liberal party. Mr Harper is hoping to change that. His apology to Chinese Canadians is one of a number of initiatives designed to impress voters from immigrant communities.

The Conservatives won only a minority of seats in the Commons in the January election, and Mr Harper has been disciplined and methodical in appealing to the voters he needs to win a majority. New Canadians are one of those groups, and he is hoping they will reward his efforts in the next federal election. This suggests there may be more apologies to come.