Iraq’s supreme court has ordered the suspension of next week’s referendum on the independence of Iraqi Kurdistan, as legal and political pressure mounted on the Kurds to call off the vote.

“The supreme court has issued the order to suspend organising the referendum set for 25 September … until it examines the complaints it has received over this plebiscite being unconstitutional,” it said.

Ayas al-Samouk, a court spokesman, said it had received several complaints, as a parliamentary source said at least eight lawmakers had called on the court to intervene on constitutional grounds.

The office of the prime minister, Haider al-Abadi, said it had also filed a complaint against the referendum in the oil-rich autonomous Kurdish region of northern Iraq on constitutional grounds.

There was no immediate reaction from the Iraqi Kurdish leader, Massud Barzani, who called the referendum and has so far resisted pressure from Baghdad, Iraq’s neighbours Turkey and Iran, and from the United States and its western allies, all opposed to the poll.

The British defence secretary, Michael Fallon, said he would try to persuade Barzani at a meeting on Monday in the Kurdish capital of Erbil.

“I will be this afternoon in Erbil to tell Massud Barzani that we do not support the Kurdish referendum,” he said at a press conference in Baghdad. “We are committed to the integrity of Iraq. We are working with the UN on alternatives to this referendum,” he added, before heading to the northern city.

The United States and other western states are backing a UN-supported “alternative” plan for immediate negotiations on future relations in exchange for dropping the referendum.

Washington argues that the vote will weaken Arab-Kurdish joint military operations that have helped to send Islamic State jihadists into retreat in Iraq and Syria. Israel is alone in openly supporting Kurdish independence.

Barzani has said a yes vote would not trigger an immediate declaration of independence but rather kickstart “serious discussions” with Baghdad. He has mustered huge popular support for the vote, with the streets of Erbil festooned with red, white and green Kurdish flags and large crowds holding nightly rallies.

The non-Arab Kurds – more than 25 million people spread across Iraq, Turkey, Iran and Syria – have long sought a state of their own.

According to analysts, Barzani is using the referendum as leverage in his Kurdish regional government’s (KRG) longstanding disputes with federal authorities in Baghdad over territory and oil exports.

The KRG has already expanded the territory it effectively controls and its peshmerga forces have seized areas outside its borders from Isis.

Oil-rich Kirkuk province, disputed by Baghdad and Erbil, has voted to take part in the referendum in defiance of the federal authorities. The government responded by sacking Kirkuk’s Kurdish governor, who has refused to leave his post. There are rumours that rival communities are stockpiling arms.

Turkey, concerned that the referendum might stir separatist dreams among its own Kurds, has threatened Erbil with “a price” to pay if the vote goes ahead. Turkey launched a military drill featuring tanks close to the Iraqi border on Monday, its army said.

The KRG’s economy is heavily dependent on oil exports via a pipeline running through Turkey to the Mediterranean.

Iran, with a sizeable Kurdish minority of its own, warned on Sunday that Iraqi Kurdish independence would mean an end to border and security arrangements with the KRG.