By Gulsen Solaker and Daren Butler

ANKARA/ISTANBUL (Reuters) – Turkish lawmakers elected seven members to a reshaped judicial authority on Wednesday, part of a constitutional overhaul backed by a referendum last month that considerably expands the powers of President Tayyip Erdogan.

Erdogan says the changes are vital to ensure stability in Turkey, which is battling Kurdish and Islamist militants and experienced an abortive coup last year blamed by Ankara on a U.S.-based cleric who had many supporters in the judiciary.

But opposition parties and human rights groups say the reforms threaten judicial independence and push Turkey toward one-man rule. Some of Turkey’s NATO allies and the European Union, which it aspires to join, have also expressed concern.

The two largest opposition parties, who say the April 16 referendum was marred by possible fraud, boycotted the overnight vote in parliament appointing seven members to a redesigned, 13-strong Council of Judges and Prosecutors (HSK) – all candidates of the ruling AK Party and its nationalist MHP ally.

The council oversees the appointment, promotion, transfer, disciplining and dismissal of judges and prosecutors.

The judiciary had previously appointed most of the HSK members but following the referendum parliament now picks seven and Erdogan a further four. The other two members of the board are the justice minister and ministry undersecretary.

“The vote has further politicized the judiciary, turning it into a totally AKP and MHP judiciary,” Filiz Kerestecioglu, a deputy from the pro-Kurdish HDP, told Reuters, saying it had decided not to participate because the process was illegitimate.

“SPIRIT OF THE REFERENDUM”

The other main opposition party, the secularist CHP, echoed that criticism.

“The party judiciary era has begun. This structure may be a complete disaster for Turkey,” CHP lawmaker Levent Gok told Reuters, accusing the ruling party of seeking to create a judiciary that was biased and dependent on it.

Prime Minister Binali Yildirim defended the vote.

“There’s no problem. It conforms to the spirit of the referendum,” the Anadolu state news agency quoted him saying.

The judicial and constitutional changes come amid a continued crackdown on suspected supporters of the Muslim cleric Fethullah Gulen blamed by Ankara for last July’s failed coup.

The HSK has already expelled 4,238 judges and prosecutors in purges targeting Gulen followers, roughly a quarter of the national total. Gulen, who has lived in the United States for decades, denies any role in the coup attempt.

Ankara says the HSK changes will prevent the judiciary falling under the control of specific groups such as the Gulenists, who Erdogan accuses of infiltrating state institutions over many years.

A CHP deputy said last month the vast majority of newly appointed judges had AKP links. The Justice Ministry rejected the allegation as slander and said the judges’ selection process complied fully with regulations.

The Venice Commission, a panel of legal experts from the Council of Europe, a rights body to which Turkey belongs, warned in March ahead of Turkey’s referendum that the proposed constitutional shakeup represented a “dangerous step backwards” for democracy. Ankara rejected the criticism.

The overhaul of the HSK is the second of the changes backed by the referendum to take effect. Another change, allowing the president to be a member of a political party, came into force this month when Erdogan rejoined the AK Party and he is set to regain the party leadership at a special congress on Sunday.

The remaining changes approved in the referendum will be implemented after a parliamentary election due in November 2019. They will enable the president to draft budgets, declare a state of emergency and issue decrees without parliamentary approval.

(Writing by Daren Butler; editing by Ralph Boulton and Gareth Jones)