SNP MPs have staged a Commons takeover of the Labour opposition benches, as they sought to push their case as the "real opposition" to the Conservatives.
The nationalists said voters who did not back the Tories at the general election deserved better than Labour's refusal to oppose the Budget.
Earlier, the SNP said Labour would pay heavily for not opposing planned welfare cuts in greater numbers.
The takeover came during a debate on Tuesday evening on the Finance Bill.
The SNP occupied the frontbench normally reserved for the official opposition. Its party members also spilled onto the second and third rows.
Raising a point of order in the House of Commons chamber, SNP MP Angus MacNeil joked that, if the furniture could not be rearranged, the parties should change the seating so the "actual opposition sits in the right place".
On Monday night, plans to cut £12bn pounds from the UK welfare budget passed their first parliamentary hurdle.
The Welfare Reform and Work Bill was backed by 308 to 124 votes, with 48 of Labour's 232 MPs voting against the package.