An attempt by British lawmakers to stop the country leaving the European Union in October without a divorce deal has passed its first major hurdle in Parliament.

The House of Commons voted 329-300 to approve the bill in principle, sending it on for further debate and another vote later Wednesday.

If the legislation is approved by the House of Commons it will go to Parliament’s upper chamber, the House of Lords. Pro-Brexit peers are threatening to try to stop it by filibustering — talking so much time runs out.

Prime Minister Boris Johnson says Britain must leave the EU on Oct. 31, with or without a deal, and plans to seek a snap election if the opposition bill becomes law.