Qatar has been cleared to host the 2022 World Cup after Fifa’s ethics committee ruled any breaches of the rules were only of “very limited scope” and closed its investigation into the controversial bidding process.

As revealed by the Guardian, the governing body’s ethics committee has decided after an 18-month investigation by the former New York district attorney Michael Garcia there is not sufficient evidence to justify stripping either Russia or Qatar of the 2018 or 2022 tournaments.

The report did note computers used by the Russian bid had been destroyed and emails were unavailable to investigators. Alexei Sorokin, who runs Russia’s 2018 organising committee, denied a deliberate cover-up. He said: “Everything we could supply to the investigation, we did.”

The decision to award Qatar the 2018 tournament in December 2010 was hugely controversial, prompting an avalanche of allegations about the way it won the bid and concerns about the searing heat in which it would be played and the treatment of migrant workers building the infrastructure underpinning it.

In a 42-page summary of Garcia’s 430-page report, Hans-Joachim Eckert, the head of the adjudicatory arm of Fifa’s ethics committee, said while there were concerns over aspects of Qatar’s bid they were not serious enough to warrant reopening the process.

“In particular, the effects of these occurrences on the bidding process as a whole were far from reaching any threshold that would require returning to the bidding process, let alone reopening it,” Eckert said.

Significantly, Eckert concludes Garcia did not find any direct link between the World Cup bid and illicit payments made by the disgraced former Asian Football Confederation president Mohamed bin Hammam, a Qatari who was banned for life for paying bribes during a campaign to unseat Sepp Blatter as Fifa president.

Garcia’s report established Hammam made “several improper payments” to high ranking African football officials and paid $1.2m to the former Fifa executive committee member Jack Warner to stop him testifying against him. It said none of these payments were related to the bid for the World Cup.

It also found Hammam offered to pay the legal fees of the banned Reynald Temarii, the Oceania confederation president who had promised his vote to Qatar’s rivals, in an effort to persuade him to appeal and so stop his replacement from taking his place and voting for Australia.

Again, Eckert found that while it was clear Hammam supported Qatar’s bid, “there is no direct link between the payments of Mr Bin Hammam to Mr Temarii.”

He adds that had Temarii taken part in the vote, it would have made no difference to the outcome. Qatar received 14 votes in the final round of voting; Australia was eliminated in the first round with just one despite spending $40m of public money on its bid.

Sepp Blatter announces Qatar as 2022 hosts in 2010 in Zurich. Photograph: Michael Probst/AP

While certain Qatari officials could yet be punished by the ethics committee, Eckert concluded: “The potentially problematic facts and circumstances identified by the report concerning the Qatar 2022 bid were, all in all, not suited to compromise the integrity of the 2018/22 bidding process as whole.”

Qatar spent hundreds of millions of dollars on a campaign of unprecedented scope and scale that included hiring such as Pep Guardiola and Zinedine Zidane as ambassadors and arranging friendlies in Doha.

Eckert says Garcia had concerns over payments intended for the Argentina FA related to a friendly with Brazil a month before the vote but concludes the arrangements were not connected to the bid.

And while he confirms Qatar’s payment of $1.8m for the rights to sponsor the Confederation of African Football Congress in Angola, thus gaining exclusive access to four of the 24 executive committee members, created a “negative impression”, he said they did not break any bidding rules.

“As regards the procedural framework for conducting bidding procedures related to awarding the hosts of the final competitions of World Cups, the investigatory chamber of the Fifa ethics committee did not find any violations or breaches of the relevant rules and regulations,” he concluded.

Of the 11 men who voted on 2018 and 2022 World Cups who are no longer on Fifa’s executive committee, only five provided answers to Garcia’s inquiry. Two could not be located at all.

Fifa welcomed the decision to close the investigation into the chaotic and confusing bidding process for the 2018 and 2022 tournaments, which virtually invited collusion by requiring the nine bidders to travel the world trying to secure the patronage of 24 Fifa executive committee members.

Incredibly, Eckert described the bidding process – which Blatter has acknowledged should not have decided two World Cups at once – was “well thought out, robust and professional”.

“Fifa welcomes the fact that a degree of closure has been reached with the chairman of the adjudicatory chamber stating today that ‘the evaluation of the 2018/2022 World Cup bidding process is closed for the Fifa ethics committee’,” said Fifa in a statement. “As such, Fifa looks forward to continuing the preparations for Russia 2018 and Qatar 2022 which are already well underway.”

Russia’s president Vladimir Putin speaks at a Russia 2018 press conference this week. Photograph: Anthony Devlin/PA

Garcia makes a series of recommendations for how the process should be reformed. Fifa has already promised to base future decisions on a vote by all 209 members at its congress rather than its executive committee.

Garcia also recommended a maximum limit of two four-year terms for Fifa executive committee members “without exception or possibility for renewal” in an effort to end the system of patronage that has hobbled attempts to reform the organisation.

He said the investigation had “noted unfortunate patterns in the history of the 24 member 2010 Fifa executive committee” and also recommended members should not be allowed to take part in votes in which they share a nationality with one of the bidding nations.

The Qatar 2022 supreme committee, which recently acknowledged the best time to play the tournament would be in winter amid a debate about the football calendar, said it would study the report in detail before responding.

The publication of the report is likely to be greeted with relief in Qatar. At the height of the Guardian’s revelations about the treatment of migrant construction workers in the tiny Gulf state and a Sunday Times investigation that sought to link Hammam payments to the Qatar 2022 bid, there was concern in Doha they could lose the World Cup.

“As we have noted in the past, we cooperated fully with the ethics committee’s investigation and continue to believe that a fair and appropriate review will demonstrate the integrity and quality of our bid,” it said.