OTTAWA: The Canadian government announced on Friday a tightening of mortgage rules to curb overspending on homes in a sluggish economy that could collapse with the burst of a possible housing market bubble. Finance Minister Bill Morneau unveiled the increase in minimum down-payment for government-backed mortgages from five to 10 per cent for homes priced over 500,000 Canadian dollars ($365,000) to address ‘potential future vulnerabilities in our housing sector’.