A Dutch psychologist has admitted making up data and faking research over many years in studies which were then published in peer-reviewed scientific journals.
Diederik Stapel, a psychologist working at Tilburg University in the Netherlands, said he had "failed as a scientist" and was ashamed of what he had done, but had been driven to falsifying research by constant pressure to perform.
The respected journal Science, which published some of Diederik Stapel's work earlier this year, issued an "expression of concern" editorial in which it said it now had serious concerns about the validity of Stapel's findings.
Stapel was suspended from his position at Tilburg University in the Netherlands in September when an investigation was launched by the university into his work.
"The official report ... indicates that the extent of the fraud by Stapel is substantial," Science's editor-in-chief Bruce Alberts wrote in the journal's online edition Science Express. The editorial was posted online late on November 1.
In a statement posted on the internet via the Dutch newspaper Brabants Dagblad this week, Stapel admitted to falsifying data and apologized for his actions.
"I have failed as a scientist, as a researcher," he said. "I have adjusted research data and faked research. Not just once, but many several times, and not just briefly, but over a long period of time.
"I am ashamed of this and I am deeply sorry."
Science published a study by Stapel and colleague Siegwart Lindenberg in April which found that people are more likely to discriminate against others when their surroundings are disordered and messy.
Alberts said he now wanted to alert readers "that serious concerns have been raised about the validity of the findings in this report."
The process of peer review, in which other scientists are asked to critique and analyze a paper before it is accepted for publication in a journal, is designed to minimize the risk that false data will get through, but it is not infallible.
British doctor Andrew Wakefield was exposed as a fraud and struck off the medical register in Britain in 2010 after his paper on links between autism and the childhood measles, mumps and rubella (MMR) vaccine was discredited and withdrawn by The Lancet, which originally published the research in 1998.
Stapel said in his statement the pressure to succeed had been too great.
"I was not able to withstand the pressure to score points, to publish, to always have to be better," he said in his statement. "I wanted too much, too fast. And in a system where there is little control, where people often work alone, I took the wrong path."