Poland's parliament has passed a law allowing border guards to immediately expel migrants who cross the border illegally.
Guards will also be given power to refuse applications for international asylum, without examination.
Human rights groups accuse Poland of wanting to legalise migrant pushbacks.
Poland and the EU have accused Belarus's authoritarian President Alexander Lukashenko of facilitating an influx of thousands of migrants.
The European Union says he is trying to destabilise neighbouring member states as a form of retaliation against sanctions.
Under international law, anyone seeking international protection must be given access to the asylum process, even if they have crossed a border illegally.
Although it is forbidden to send people back to where their wellbeing may be in danger, rights groups have accused Poland of pushing back migrants for months.
At least six migrants have been found dead near the border with temperatures now falling below freezing overnight.
The newly approved legal amendment must now be signed into law by Polish President Andrzej Duda, an ally of the government.
Since August, there have been more than 16,000 attempts to cross the Belarusian border illegally compared with just 120 for the whole of last year, Poland's border agency has said.
Fellow EU states Lithuania and Latvia have also seen massive increases in migrants from Middle Eastern and Asian countries trying to enter illegally from Belarus since the start of the summer.
Belarus has been accused of inducing migrants to fly there on the false promise of legal entry to the EU.
The Belarusian government has denied the allegations and blames Western politicians for the situation on the border.
Poland has erected a temporary fence of razor wire along stretches of its border and on Thursday the parliament in Warsaw backed a plan to build a border wall.