Moscow (CNN) -- The crew was at fault in a Polish plane crash that killed the country's president and nearly 100 other people last April, a Russian-led investigation found Wednesday.
The crew should have decided to divert to another airport in light of "repeated and timely" warnings about bad weather in Smolensk, Russia, the Interstate Aviation Committee concluded.
The presence of a Polish Air Force commander in the cockpit may also have contributed to the crash, the IAC said, noting that he had alcohol in his blood at the time of the crash.
Polish President Lech Kaczynski, his wife and many top Polish officials died in the crash as they headed to a memorial service to mark a World War II massacre.
Jaroslaw Kaczynski, Lech Kaczynski's twin brother, told reporters Wednesday that the Russian inquiry into the accident was biased and that there was no proof to support the main thesis of the report.
"Anyone who knows Russia could have guessed that this is what the report would look like. The report gives no answers to the most important questions," he added.
The crew of the Polish presidential plane was under psychological pressure to land the plane at Smolensk, fearing Kaczynski would react negatively to a decision to divert the plane, IAC chair Tatyana Anodina said. She spoke in a news conference broadcast live by Russian state television.
The investigation did not find any evidence that the president ordered the pilots to land at Smolensk, she said, but the air force commander, Gen. Andrzej Blasik, may have influenced them.
The presence of Blasik in the cockpit "up until the plane hit the ground had a psychological influence on the plane's commander's decision to take an unjustified risk by continuing the descent with the predominant goal of landing against the odds," Anodina said.
Forensic medical examination found 0.6 ppm (parts per million) of alcohol in his blood, she said. That amount would have resulted from ingesting about 3.5 to 4 ounces of alcohol, and would be over the legal limit of intoxication for drivers.
The crew also did not have sufficient training for landing in bad weather, Anodina said.
The IAC will publish its report in Russian, Polish and English, "given the high profile of this case and the importance of making the investigation results available to the public," IAC technical commission chairman Alexei Morozov said at the same news conference.
IAC officials said they are prepared to provide the results to an international investigation or auditors.
The final report has been handed to Polish officials, Anodina said.
The Russian-made Tupolev Tu-154 plane crashed on April 10, 2010, in Russia's Smolensk region west of Moscow, killing everyone aboard as they headed to the village of Katyn to commemorate the massacre in which some 22,000 Poles were executed by the Soviet secret police.
The IAC is a special aviation watchdog authorized to investigate plane accidents in Russia and other countries of the former Soviet Union.
Journalist Andrew Bobinski contributed to this report.