London (CNN) The British government has the power to unilaterally halt the Brexit process, a top European legal adviser has said, delivering a significant boost to campaigners who want the UK to remain in the EU.

In an opinion prepared for the European Court of Justice (ECJ) in Strasbourg, the advocate general said the UK could stop the two-year legal countdown invoked under Article 50.

The UK had argued that the Article 50 notification could only be withdrawn with the agreement of all 27 remaining EU member states.

Announcing his conclusion Tuesday , Advocate General Campos Sanchez-Bordona declared that Article 50 "allows the unilateral revocation of the notification of the intention to withdraw from the EU."

Judges must now decide whether to accept the advocate general's advice, as they do in most cases.

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