Former U.K. Prime Minister Sir John Major has said he will join a legal action to block Prime Minister Boris Johnson suspending parliament.

“I promised that, if the Prime Minister prorogued Parliament in order to prevent Members from opposing his Brexit plans, I would seek judicial review of his action,” the former conservative prime minister said in a statement.

The controversial plans to suspend or “prorogue” parliament were announced by the U.K. government on Wednesday morning, effectively locking lawmakers out of the building for several weeks in early September. Several leading politicians have expressed concerns that the move would prevent lawmakers from passing legislation regarding Britain’s scheduled exit from the E.U. on Oct. 31, and allow Johnson to force through a controversial “no deal” Brexit. (Johnson has denied this is his motivation.)

Major has previously warned that proroguing parliament would mean “heading in a very dangerous territory.” Speaking at Chatham House in June, Major said: “I cannot imagine Mr Disraeli, Mr Gladstone, Mr Churchill or Mrs Thatcher even in their most difficult moment saying let us put parliament aside while I carry through this difficult policy that a part of my party disagrees with.”

Johnson has pledged to leave the E.U. by the scheduled departure date of Oct. 31, with or without a deal, and the government has said the five-week suspension will still allow time to debate Brexit.

But the decision prompted a backlash from lawmakers and opponents of a no-deal Brexit – and the shock it could bring. The move sparked protests across the country, resignations, and a petition with over 1.5 million signatures. Johnson’s decision has been described as “a threat to democracy” and “a constitutional outrage” both by opposition leaders and by members of Johnson’s conservative party.

Major, who was prime minister from 1990 to 1997, has joined a challenge launched by anti-Brexit campaigner Gina Miller, who previously used the courts to force parliament to pass legislation to trigger the Article 50 Brexit process.

“In the view of imminence of the prorogation – and to avoid duplication of effort, and taking up the Court’s time through repetition – I intend to seek the Court’s permission to intervene in the claim already initiated by Gina Miller, rather than to commence separate proceedings,” Major said in the statement.

Miller said a court hearing will be held on Sept. 5. Judges will decide if the government has allowed sufficient time for a debate on a no-deal Brexit.

In a separate legal challenge brought by lawyers of 75 anti-Brexit lawmakers, a judge temporarily rejected calls to to block Johnson’s decision of proroguing parliament on Friday.

Judge Lord Doherty brought forward the hearing to Sept. 3.

“I’m not satisfied that it has been demonstrated that there’s a need for an interim suspension or an interim interdict to be granted at this stage,” he said. “I’m going to move the substantive hearing forward to Tuesday. Weighing consideration in the balance, it’s in the interest of justice and in the public interest that it proceeds sooner rather than later.”

The U.K. government is also facing a legal action in Belfast.

Write to Julia Webster at julia.webster@time.com.