Germany's outgoing lower house of parliament began a special session on Thursday to debate a 500 billion euro fund for infrastructure and sweeping changes to borrowing rules in Europe's largest economy to bolster defence.

Germany's outgoing parliament is set to meet on Thursday to discuss a constitutional amendment to enable a massive government spending package on defence and infrastructure, despite ongoing wrangling among lawmakers.

A senior Greens legislator said there would still be a sufficient, albeit different, majority to reform Germany's debt brake once the newly elected parliament had been seated, in an indication they might continue to block conservative chancellor-in-waiting Friedrich Merz's plan for reform.