All opposition parliamentary groups in Bulgaria are gathering signatures to petition the Constitutional Court against recently-approved amendments to the law on municipal elections.

More than 50 of 240 MPs had signed up so far, Bulgarian National Radio (BNR) reported.

The opposition objects to the amendments having been put to a third reading vote, when the constitution requires two stages of voting. The residence principle, which says that a voter should have lived in a municipality for a certain period to be eligible to vote, “tripped up” the amendments. The principle was approved on second reading with only one vote in favour and then was put to the vote for a third time.

Ivan Sotirov, an MP for centre-right opposition party the United Democratic Forces, said that there was already a Constitutional Court precedent on the question of three rounds of voting.

The opposition will wait until the amendments are promulgated and will then petition the court to overturn the clauses on the residence principle.

According to Sotirov, the opposition’s sole goal was clarity about electoral procedures. Bulgarians, along with EU citizens permanently resident in Bulgaria and therefore eligible to vote, are to go to the polls on October 28 to elect city and town councillors and mayors.