Malta believes a new migration pact being proposed by the European Commission is "complex and vague" and the country has joined Italy, Greece and Spain in pushing for mandatory relocation mechanisms to be introduced into EU law.
News wire AFP reported on Wednesday that prime ministers of the four countries, among them Malta's Robert Abela, expressed their concerns about the proposed new migration plan in an undated memo.
A diplomatic source said it was addressed to European Commission chief Ursula von der Leyen, European Council head Charles Michel and German Chancellor Angela Merkel, whose country holds the EU's rotating presidency.
While backing the efforts made to reform Europe's asylum rules, the four governments said "mandatory relocation should remain and be pursued as the main solidarity tool".
Ever since a migration crisis in 2015 that saw over a million asylum-seekers enter Europe, the EU's refugee and migration rules have been exposed as deficient.
As the EU's southernmost state, Malta sits on the external border of the EU and serves as a key entry point for migrants making asylum claims, whether they be refugees or economic migrants seeking better opportunities.
Spain, Italy and Greece also lie along the EU's southern border.
What is the proposed new plan?
The Commission wants to overhaul the rules so that the asylum-seekers are shared out across the 27 member countries and not left the responsibility of Greece, Italy, Malta and Spain.
Aware that some countries, mainly eastern EU states, resist that, the new pact proposes they contribute funds instead to help the others taking in asylum-seekers.
At the same time, border pre-screening procedures would be stepped up to stop and return economic migrants to their home countries.
When the plan was first unveiled, Foreign Affairs Minister Evarist Bartolo had described it as a positive first step but warned that "there are issues to be addressed".
The memorandum seen by AFP called on more work to define the burden-sharing.
"We believe that the solidarity rules and the related commitment of all Member States must be clearly defined," it says. "The front-line Member States cannot face the migratory pressure on the whole European Union."
It added that the notion of building border detention centres to pre-screen arrivals was not feasible nor in line with human rights or international asylum law.
In terms of returns, the four urged closer political dialogue with countries from where Europe's irregular migrants originate, with "positive incentives" to have them accept returnees.
Finally, the memorandum said it backed boosting channels for legal immigration into the EU - something that already features in the Commission's proposed pact.
The pact was presented in September, opening negotiations between member states and MEPs that could run for months or years before a final text is arrived at.