BERLIN (Reuters) - Germany's population rose to 81.1 million people in 2014, the fourth annual increase in a row, boosted by the highest level of net migration in more than two decades, the Federal Statistics Office said on Wednesday.

Germany, the European Union's most populous country and also its largest economy, had a population of 80.8 million at the end of 2013.

As in much of Europe, Germany's population is ageing fast, with as many as 215,000 more deaths than births last year, but that was more than offset by an influx of about 470,000 migrants.

The number of migrants was the highest since 1992 when immigration peaked following the collapse of communism in eastern Europe and war in the former Yugoslavia.

A large influx of immigrants and asylum seekers - many from Syria - over the last few years has alarmed many Germans and become a potent political issue, increasing support for a new right-wing political party, the Alternative for Germany (AfD).

It has also fuelled grassroots anti-immigrant movements such as PEGIDA (Patriotic Europeans Against the Islamisation of the West), which holds regular rallies in the eastern city of Dresden and wants to expand to other German towns and cities.

Chancellor Angela Merkel's government was due to publish on Wednesday a report showing that more than three quarters of migrants to Germany in 2013 came from Europe, with the biggest number from Poland.

Last year, there was a sharp rise in the number of people arriving from other new EU member states Romania and Bulgaria.