Why is there such a backlash against immigrants in the UK?

Canada has a HUGE amount of open space compared to the UK. Canada needs skilled immigrants while in the UK we are overflowing with people looking for jobs in many areas hence our current high unemployment rate. I personally think that Canada and the UK are great welcoming countries that go for multiculturalism and this is slightly more true for Canada as there have been more racial incidents involving immigrants in the UK but then and again we have a larger population but a much smaller land area!