Omer Faruk Gergerlioglu, 55, was stripped of his seat and arrested in March after being convicted of "spreading terrorist propaganda" in a social media post.

"Praise be to God," Gergerlioglu tweeted as the decision to readmit him was read out in parliament.

He represents the pro-Kurdish Peoples' Democratic Party (HDP), which the government is trying to ban over its alleged links to outlawed militants waging a decades-long insurgency against the Turkish state.

He was sentenced to two-and-a-half years in prison for re-posting an article in 2016 in which the militants called on the government to take a step toward peace.

Gergerlioglu has long been an irritant for President Recep Tayyip Erdogan's government, but his advocacy for female detainees subjected to strip searches particularly angered Turkish officials last year.

The HDP denies formal ties to the Kurdistan Workers Party (PKK), which is regarded as a terrorist organisation by Turkey, the US and EU.

But the constitutional court last month agreed to hear a government lawsuit attempting to disband the HDP on terror-related grounds. Analysts believe the trial could last at least a year.

The HDP has already seen scores of its current and former members arrested in a government crackdown that followed a failed coup attempt against Erdogan in 2016.

Turkey's Western allies have been alarmed by Erdogan's push against the party, warning that it threatened to further undermine ties.