The Premier League has been urged to re-examine assurances given by Newcastle's Saudi owners that the Middle East state would not have control of the club following the filing of a new court document in the United States.

The document filed earlier this week has raised fresh questions about the level of separation between the Saudi state and the Public Investment Fund (PIF), whose governor Yasir Al Rumayyan is also chairman of Newcastle.

A brief filed in a court case involving the PGA Tour and LIV Golf describes the PIF as "a sovereign instrumentality of the Kingdom of Saudi Arabia" and Al Rumayyan as "a sitting minister of the Saudi government".

The Premier League approved the PIF-led takeover of Newcastle in October 2021 after receiving "legally-binding assurances" that the Saudi state would not have control of the club. Now human rights group Amnesty International is calling on the league to ask new questions of Newcastle's owners.

"It was always stretching credulity to breaking point to imagine that the Saudi state wasn't directing the buyout of Newcastle with the ultimate aim of using the club as a component in its wider sportswashing efforts," Peter Frankental, Amnesty UK's economic affairs director, said.

"There's an unmistakable irony in the sovereign wealth fund declaration emerging in a dispute about another arm of Saudi Arabia's growing sports empire, but the simple fact is that Saudi sportswashing is affecting numerous sports and governing bodies need to respond to it far more effectively.

"The Premier League will surely need to re-examine the assurances made about the non-involvement of the Saudi authorities in the Newcastle deal, not least as there's still a Qatari bid for Manchester United currently on the table."

The PIF is chaired by the Saudi Prime Minister, Crown Prince Mohammed Bin Salman, with eight of the nine PIF board members listed on the fund's website as being either a minister or a royal advisor. Al Rumayyan is the only exception,but now the court document describes him as a minister too.

Frankental added: "In the 18 months since the Newcastle purchase, the human rights situation in Saudi Arabia has deteriorated markedly, with scores of executions after unfair trials, courts jailing peaceful critics, and the authorities continuing to block accountability for Jamal Khashoggi's murder."

The Premier League and Newcastle have declined to comment.

The league's chief executive Richard Masters said in November 2021 that if his organisation found evidence there was state involvement in the running of the club the consortium could be removed as owners.

The PIF has also declined to comment. It is understood to have given legal undertakings to the Premier League that there would be no state control over the club.

The PIF is challenging an order to produce documents and testify in the LIV Golf case.

A document seen by the PA news agency and dated February 28 states: "The order is an extraordinary infringement on the sovereignty of a foreign state that is far from justified here.

"The PIF and His Excellency Yasir Othman Al Rumayyan are not ordinary third parties subject to basic discovery relevance standards.

"They are a sovereign instrumentality of the Kingdom of Saudi Arabia and a sitting minister of the Saudi government, and they cannot be compelled to provide testimony and documents in a US proceeding unless their conduct - not LIV's or anyone else's - is truly the 'gravamen' of the case."

Sources linked to Qatari businessman Sheikh Jassim bin Hamad Al Thani say he is bidding alone for Manchester United, with no assistance from the Qatari state, sovereign wealth funds or other individuals.

Newcastle boss Eddie Howe insists he has to concentrate on his players after refusing to become embroiled in a new row over the club's ownership.

Asked about the latest development, head coach Howe said at a press conference on Friday: "For me, my job is training the players, trying to get them in the best physical, mental, tactical condition to win the game.

"The minute I deviate from that is the minute I go into dangerous waters for me and I waste energy in areas that don't help the players. For me, my main job is to coach the players and get them in the best place possible."

Asked further if the club's owners - PIF hold an 80 per cent stake at St James' Park - needed to speak to clarify matters and lift the pressure to do so from his shoulders, Howe added: "Obviously the focus comes on me because I'm sat in front of you every week.

"But I don't think - as I've said many times - it's a conversation for me to necessarily brief on these matters because I'm not really qualified to do it."

Newcastle co-owner Amanda Staveley says she's confident the club's majority shareholders PIF won't have their heads turned by the 'for sale' signs at Manchester United and Liverpool.

Speaking at the Finacial Times Football Summit, Staveley said her consortium chose Newcastle due to the fact the price was less than 10 times what Man Utd and Liverpool are for sale at.

"When we looked at Newcastle, we were very clear we wanted a club with a passionate fanbase. We got that," she said. "We also wanted a club we could buy affordably because we [Staveley and husband Mehrdad Ghoudoussi] are also partners with PIF.

"We are not that wealthy. We're the poor partner and that helps govern a lot of decisions.

"We didn't go for the wonderful Tottenham and Chelsea and Liverpool. I'm a massive Liverpool fan and we tried to buy them but we walked into a Newcastle game and said 'why spend X billion when you can spend £350m [on Newcastle]?'"

But when asked if PIF would switch their interest to one of the global powerhouses due to their availability, she added: "No, I don't think so. I can't speak for PIF but I really can't see that happening. We've built in the last year from 11th to hoping we have a chance of the Champions League."