Alexander told 51 new Canadians the first overhaul of the Citizenship Act in 36 years is meant to strengthen the value of a Canadian passport and to improve the efficiency of how citizenship is acquired.
He said the new rules will clamp down on what he called Canadians of convenience by making it harder to obtain citizenship.
Permanent residents will have to maintain a physical presence in Canada for four out of six years before applying for citizenship, compared with the previous requirement of three out of four years.
Alexander said permanent residents who are members of the Canadian Armed Forces will have a fast track to citizenship.
As well, citizenship will be revoked from dual nationals who are members of groups engaged in an armed conflict with Canada or convicted of terrorism, high treason or spying.
"If you're a dual citizen — and we expect this will only ever apply to an extremely lower number of people — or a permanent resident convicted of terrorism, high treason, treason or spying offences, then you will forfeit your right to hold Canadian citizenship," said Alexander.
"We want to send a strong message that people who commit acts against Canada will not ... continue to enjoy the privilege of calling themselves Canadian citizens."
As eligibility requirements increase, the government has indicated it would simultaneously speed up processing times for applications by streamlining decision-making.
It's hoped the change will help drastically cut a backlog of citizenship applications, which currently sit at more than 320,000 files. Processing times stretch to as much as 36 months.
By 2015-2016, the government said it hopes to process successful applications in less than a year.