The Commission called on Austria, Germany, Denmark, Sweden and Norway, which still have temporary controls in place at some of their borders, to phase them out and replace them with proportionate police checks.

"Whilst the overall situation continues to stabilise, there are still a significant number of irregular migrants and asylum seekers in Greece," said the Commission.

"That is why, as a precautionary measure and whilst alternatives are put in place, the Commission is recommending that the Council prolong controls for the last time, meaning they will have to be lifted in six months' time."

In this period, controls should only be carried out in a targeted and limited manner and only as a means of last resort.

The countries are urged to apply alternative measures that can provide the same level of security, such as proportionate police checks in border areas and along main transport routes.

To that effect, the Commission also presented a recommendation on proportionate police checks and police cooperation in the Schengen area.

The Commission believes that proportionate police checks could prove more efficient than internal border controls as they can be applied in a more flexible manner and are easier to adapt to evolving risks.

Member states are advised to give precedence to police checks before introducing or prolonging temporary internal border controls.

Brussels moreover urged strengthening cross-border police cooperation, for example through joint police patrols in cross-border trains, joint threat analyses and enhanced cross-border information exchange.

To effectively prevent irregular secondary movement without having to reintroduce internal border controls, member states are advised to fully apply existing bilateral agreements that allow for the swift bilateral return of third-country nationals.

Upon the latest extension First Vice-President Frans Timmermans promised: "This means that in six months' time we will get back to a fully functioning Schengen area without internal border controls."

But a similar promise made by Migration Commissioner Dimitris Avramopoulos upon the previous extension in January had not come true.

Slovenia has been protesting that temporary checks imposed by Austria on the shared border are unwarranted.

The Commission's recommendation on the extension of temporary border controls now need to be endorsed by member states with a qualified majority needed for approval.

"This is the last time a prolongation of these controls is legally possible under EU rules," said the Commission.

The reinstatement of controls on internal Schengen border was prompted by the migration crisis in May 2016. The Commission first recommended the measure for six months, extending it by three months in November and by another three months in January, with a six-month extension following today.

Temporary controls in case of exceptional circumstances constituting a serious threat to the overall functioning of the Schengen area may be extended up to three times.

However, internal controls may also be introduced based on different legal grounds, which is why it is impossible to rule out a continued implementation of the measure.

A member state may impose controls unilaterally, that is without the Commission's recommendation, in the event of unforeseen events constituting a threat to public order and internal security.

Brussels was not expected to propose lifting internal border checks before German elections. Due to the continued threat of terrorism, it is also questionable whether the measure would be scrapped later on.

Austrian Interior Minister Wolfgang Sobotka has recently commented that internal border controls within the Schengen area should be extended indefinitely.