The U.K. Serious Fraud Office has further delayed a decision on whether to bring criminal charges against Barclays Plc and its former executives over the bank's dealings with Qatar clients in 2008.

The SFO's long-running investigation centers around Barclays' side-arrangements with Qatari investors at the time of its fundraising in 2008, which the bank conducted in a last-ditch effort to avoid being put under government control.

The regulator's decision is now expected in mid-June after it missed its late-May deadline, itself a delay from a March deadline, the Financial Times reported.

The new deadline means that any charging decision will not be made until after the June 8 general election.

The delay comes after the U.K.'s ruling Conservative Party pledged in its election manifesto to roll the SFO into a wider crime-fighting agency if it wins. The SFO, however, stressed that the reasons for the postponement of the deadline were purely operational, according to the May 26 report.

In March, the Financial Conduct Authority reopened its investigation into the bank's 2008 cash call, with an aim to reach a decision by early May; however, the FCA was reported to have postponed its decision regarding the probe after law firm Simmons & Simmons, which is acting for Barclays, found thousands of new documents relating to the fundraising.