Barclays' chief executive Jes Staley faces an uphill battle to retain shareholders' support at the bank's annual general meeting (AGM) later this week.

Two of the FTSE 100-listed lender's main shareholders have strongly criticised Staley for his "poor judgment" over two separate incidents in recent weeks and the 60-year-old could face further scrutiny at the AGM on Wednesday (10 May).

Last month, the Financial Conduct Authority (FCA) began a formal investigation into Staley's handling of the bank's whistleblower scandal and Institutional Shareholder Services told investors to opt against re-electing the CEO because his personal involvement and accountability" in the matter.

Barclays' board, led by chairman John McFarlane, has publicly reprimanded him for his actions, although Staley has insisted the board remained fully supportive and gave him "unanimous confidence".

However, Wednesday will be the first time the Barclays boss faces shareholders following the scandal and some suggest the situation could unravel.

According to the Sunday Times, one of the lender's major shareholders said Staley's position could become "untenable" should new details emerge.

"Either you think that he has done something materially wrong and shouldn't be there, or you think that he was foolish but has been formally reprimanded and penalised through the wallet and you still think he's the right man to run the company," another prominent Barclays shareholder was quoted as saying by the Telegraph.

According to the FCA, Staley's attempts to unmask the whistleblower, who raised concerns about a senior employee at Barclays who had been recruited earlier in 2016, were in contravention of the bank's procedures on whistleblowing.

Barclays's board hired law firm Simmons & Simmons to investigate the letters last year, but it said that it only came to know of the chief executive's efforts to identify the author in early 2017.

Staley has since apologised for his conduct, stressing his was a "honest" mistake and Barclays said the American banker, who joined the lender in 2015, will have to accept a "very significant compensation adjustment".

However, a source closed to lender was reported as saying by the Sunday Times that Staley's pay could be "clawed back" even more, should the lender be fined for its role in the controversy.

Separately, Staley is also under scrutiny for his role in a legal dispute between KKR, one of the bank's largest clients, and his brother-in-law. In 2014, the Barclays boss' wife, Debora Nitzan Staley, and her brother, Jorge, sold their shares in Aceco, a Brazilian data centre operator founded by their father, to KKR in a deal that valued Aceco $700m (£540m).

However, KKR was forced to write off its entire investment due to the financial crisis that has hampered the Brazilian economy over the last three years. The firm has since claimed it was defrauded, an accusation which has swiftly been denied by Staley's brother-in-law.

The Barclays CEO was himself accused of a conflict of interest by KKR after he intervened on Niztan's behalf, although he's always maintained that he conducted himself properly. However, as a result of the fallout, KKR has since taken new business away from the London-listed banker.