The European Commission is to sue Poland, Hungary and the Czech Republic at the European Court of Justice (ECJ) for refusing to take in asylum seekers.
The commission, the EU’s executive body, accused the three countries of “non-compliance with their legal obligations on relocation”.
The Luxembourg-based ECJ could impose heavy fines.
A relocation plan was launched by the EU in 2015 in response to a large influx of migrants and refugees.
The move was an attempt to relieve pressure on Greece and Italy where the vast majority of migrants were arriving.
However, the Czech Republic has accepted only 12 of the 2,000 asylum-seekers it had been designated, while Hungary and Poland have received none.
The commission launched infringement procedures against the three states in June and warned them last month that further action was likely.