Unnoticed and unremarked upon by the election campaign, 400 people drowned in the Mediterranean last week. They were fleeing, from Libya, from the Middle East, from Egypt, from Syria, trying to reach Europe by crossing the sea.

The journey is treacherous; most of the refugees aren’t seamen, most of the boats are rubber dinghies. Why is it happening? The crossings aren’t new, but the death toll is.

Until November of 2014, the Italian fleet carried out search and rescue operations in the Mediterranean, with the help of €30m from the European Union. The operation – called “Mare Nostrum”, or “Our Sea” after the Roman term for the Mediterranean – saved the lives of an estimated 150,000 refugees who would otherwise have drowned while making the crossing.

But the cost to the Italian government – close to €9m a month – far outstripped the European subvention, and other member states, facing pressure from anti-immigration sentiment at home, were reluctant to continue funding the scheme, including the British government. Baroness Anelay, a Conservative minister at the Foreign Office, told the House of Lords that there were concerns that continuing the rescue operation could be a “pull factor”, drawing more migrants to make the dangerous journey.

The reality is that the ships of the Italian fleet weren’t a “pull factor” of any sorts. When the scheme was brought to an end, the Guardian found that people coordinating the crossings were unaware that the rescues existed. What matters is the “push factor”; of increasing repression in Egypt, of violence in Libya, of the march of Isis in Syria. Since the cancellation of Mare Nostrum, crossings have continued unabated. The only appreciable change is the rising death toll.

The good news is that the European Commission will discuss restoring Mare Nostrum on May 27. The chances for bringing back the rescue operations are good but the stance of the next British government will be vital. Ed Miliband and Nick Clegg have both committed to push to restore the scheme. You can add your voice by signing the Save the Children petition here.