BRATISLAVA (Reuters) - Slovak Interior Minister Robert Kalinak, a close ally of Prime Minister Robert Fico, faced a second vote of no-confidence on Thursday in the space of just three weeks, putting pressure on the government as it takes over the rotating European Union presidency.

Thousands of Slovaks protested earlier this week to demand Kalinak’s resignation over a business transaction with a real estate developer, one of whose companies is being investigated over allegations of tax fraud.

Interior ministers play a key role in forming EU policy in the migration crisis, an issue Slovakia said would be high on its EU presidency agenda after over 1 million migrants and refugees reached Europe, mostly by sea, last year.

Kalinak, number two in Fico’s leftist Smer party, has the confidence of the governing coalition and is expected to survive the evening vote. But the opposition says there will be a protest every Monday until he quits.

Kalinak has said he bought a 17 percent stake in one company from the developer, Ladislav Basternak. He has denied any wrongdoing.

Kalinak’s ministry is responsible for the police, and the opposition argues that this is preventing an independent investigation into tax fraud allegations involving a separate firm that was owned by Basternak.

Fico backed Kalinak on Thursday, accusing the opposition of trying to spoil Slovakia’s EU presidency.

“Slovakia is a trustworthy country and the fact it will hold an informal summit of EU prime ministers and heads of states on Sept. 16 is a proof of its credit,” Fico told lawmakers.

Fico himself lives in a rented apartment owned by Basternak in central Bratislava. He has rejected opposition calls to move out.

Reuters could not reach Basternak for comment. His companies do not list phone numbers and he did not immediately respond to a request for comment sent by email. He has not been quoted in Slovak media in relation with the investigation in recent weeks.

Fico’s Smer party won a second consecutive term in an election in March but lost its parliamentary majority and had to form a coalition with three other parties.

Slovakia has been a strong critic of EU attempts to stem the flow of refugees fleeing conflict from countries in the Middle East and North Africa, and has sued the EU over a quota system to distribute asylum seekers agreed by a majority vote last year.

It has promised to be an “honest broker” as it leads the EU until the end of the year, saying it will focus, among other things, on strengthening the bloc’s borders.