Fifa's chief ethics investigator will not consider millions of documents underpinning a new wave of corruption allegations surrounding the award of the 2022 World Cup to Qatar.

Michael Garcia promised to complete his work by next week, but his decision not to examine the documents obtained by the Sunday Times could undermine faith in his investigation at a crucial time.

It is understood that Garcia has not asked for the documents, said by the newspaper to number hundreds of millions of files including emails and accounts linked to the Qatari former Fifa vice-president Mohamed bin Hammam.

Those familiar with the cache say it would be impractical for him to examine them before his new deadline, days before the 2014 tournament begins in Brazil on 12 June. Qatar has faced calls to be stripped of the 2022 World Cup in the wake of fresh allegations that Bin Hammam used a $5m (£3m) slush fund to not only buy goodwill for his tilt at the Fifa presidency but to aid the 2022 bid.

"After months of interviewing witnesses and gathering materials, we intend to complete that phase of our investigation by 9 June 2014, and to submit a report to the adjudicatory chamber approximately six weeks thereafter," said Garcia.

"The report will consider all evidence potentially related to the bidding process, including evidence collected from prior investigations."

Garcia has spent more than a year and £6m travelling the world to interview those involved in the race to host the 2018 and 2022 tournaments and investigate allegations of bribery and corruption.

He has interviewed representatives from all nine of the bidding nations, including a summit with a Qatari delegation on Monday. His findings will inform the Fifa president Sepp Blatter's decision on whether to order a revote.

But the fact that Garcia will not properly analyse the evidence from the Sunday Times database, which will form the basis of further allegations about the Qatar bid in the weeks to come, will raise concerns that he has already formed a view.

Jim Murphy, the shadow secretary for international development, said: "If the Garcia investigation refuses to accept the Sunday Times evidence the process will be a sham and Fifa will be forever tainted. Corruption must be tackled."

Meanwhile, David Cameron, who was one of the so-called "three lions" involved in the final push in December 2010 for England's doomed £21m bid to host the 2018 World Cup, said Garcia's inquiry should be allowed to take its course.

"We will see what happens with this inquiry into the World Cup. And who knows what the chances may be for the future," the prime minister said.

"There is an inquiry under way, quite rightly, into what happened in terms of the World Cup bid for 2022. We should let that inquiry take place rather than prejudge it.

"My memories of that bidding process are not happy memories in terms of the way the whole thing was arranged and the role of Fifa."

Cameron said he, David Beckham and the Duke of Cambridge were assured by numerous Fifa members of their support.

But in the end England secured only one vote among the 22 executive committee members apart from that of their own Fifa vice-president, Geoff Thompson.

He added: "I'll always remember Beckham saying to me afterwards: 'I can cope with being lied to but I can't cope with people lying to the prime minister and the future king'."

Two of the failed bidders for the 2022 World Cup, Australia and Japan, have joined calls for the bidding race to be rerun. Both exited in the early rounds of the voting process, with Qatar defeating the US 14-8 in the final runoff.

Yuichiro Nakajima, the head of Japan's unsuccessful bid to host the 2022 World Cup, said the allegations should be investigated by Garcia and backed calls for the bid process to be rerun. "All of this points to the need for a major reform of how Fifa is governed," he said.

The chief executive of the Football Federation Australia, David Gallop, said the new revelations were a serious development and told local media his federation had been involved in interviews and the production of documents.

"It's too early to say whether that reopens the door of anything that happened a few years ago in terms of Australia's position but it's a bit of a 'watch this space' at this stage," he said.

"We've been heavily involved in this now for many months in terms of the investigation that Mr Garcia is carrying out. We've got people who've been involved for some time now."

The Qatar 2022 bid committee has denied any wrongdoing and said it had nothing to hide. "We say again that Mohamed bin Hammam played no official or unofficial role in Qatar's 2022 bid committee."

Mark Pieth, the chairman of Fifa's recently disbanded independent governance committee, said the vote should be rerun. He told CNN: "What I think is that it's going to shake Fifa to the foundations, because it's the first time that an institution like Fifa has to ask itself whether it should totally rerun the decision of a host, the hosting decision, and the consequences could be massive, could be about billions of dollars."

Meanwhile, Michel Platini, the president of the European football federation, Uefa, is discussing the possibility of leading a sit-down protest when Blatter announces his intention to stand again as Fifa's president in Brazil next week.

Platini, who is increasingly considered unlikely to challenge Blatter for the top job, may ask the heads of the 54 European FAs to remain seated when the majority of the other 155 Fifa members rise to acclaim the announcement as a means of registering disapproval at Blatter's decision to stand for a fifth term despite earlier promising to stand down.