The far-right Alternative for Germany (AfD) and the Left Party jointly secured one third of seats in the new parliament, enough to block a loosening of Germany's debt brake - a mechanism some investors and political parties say stymies economic growth.

The leader of the far-right Alternative for Germany (AfD), the second largest party in parliament after Sunday's election, said Germany's likely next chancellor would be held hostage by left-wing parties that would seek to loosen tough fiscal rules.

Germany's conservatives won the national election on Sunday, while the far-right Alternative for Germany came in second, its best ever result.