The far-right Alternative for Germany (AfD) will introduce internal border checks if it takes power in two states following elections in September, co-leader Tino Chrupalla told national public broadcaster ARD on Sunday.
The anti-immigration party would also immediately suspend the mechanism agreed for distributing migrants between the 16 states, he said.
"That for example would be a programme for the first 100 days, where we say quite clearly: restrictive border controls," Chrupalla said.
The AfD would no longer be bound by the migrant distribution agreement, he insisted. The agreement is based partly on the tax income and partly on the population of the respective states.
Leaving the agreement was important in order to put pressure on the federal government to change its policy, he said. "We have to ensure that migration in its current form finally belongs to the past."
The AfD is riding high in the polls in the states of Thuringia and Saxony, where observers believe forming a workable coalition government without them could be all but impossible. To date the other parties have refused to cooperate at state level with the AfD.