The scheme, endorsed by EU leaders in June, means that Brussels will directly email all new proposals and consultation papers to national parliaments, "inviting" them to react at an early stage.

A commission official said the first documents will be transmitted to parliaments as early as next week, with communication commissioner Margot Wallstrom set on Wednesday to symbolically fire off the first email.

Take note, not review

The early warning initiative reflects national MPs' growing ambitions to play a stronger role in overseeing EU legislation.

At present deputies tend to raise the alarm only at a stage when the legislation is already too far down the Brussels the lawmaking machine.

The plan resembles the so-called "yellow card" procedure foreseen in the shelved EU constitution stating that the commission should review a legislative proposal, if at least one third of national parliaments believe the proposal falls outside EU competencies.

But a commission source said that with the constitution being on ice, "the question of review [of law proposals] is not on the agenda," adding that Brussels will only "take note" of national parliamentarians' wishes.

In its reply to comments from national deputies, the commission will "reiterate the goal of its proposals" but not offer "new arguments."

"We cannot do anything which would anticipate the constitution," said a commission source.

Brussels is keen to avoid criticism of "cherry-picking" from the comatose charter, the future of which is highly controversial among EU member states.

Test case on divorce law

But some national parliaments' EU affairs chiefs are set to ask for more than just consultation at a planned meeting with commissioner Wallstrom in Helsinki on 11 September.

"I'm not sure that the commission can go ahead with a proposal which is disliked by 25 national parliaments," said one national parliament source.

Member states' parliaments earlier this year decided to jointly scrutinize two of this year's commission proposals - on cross-border divorces and liberalisation of postal services - where they suspect the commission could over-regulate.

Brussels' planned divorce law, presented just before the summer break, will serve as the first test case of national parliaments' watchdog aspirations, with national parliaments' common Brussels secretariat, COSAC, setting a 27 September deadline for reactions.

It is however unclear to what extent MPs will participate in the common move, with the Swedish parliament for example focusing on elections at home.