Government interference was partly to blame for delays in issuing school Sats results in England last year, MPs say.
The Commons schools select committee said the Department for Children, Schools and Families involved itself too much in the detail of the testing.
Last year, hundreds of thousands of 11 and 14-year-olds were left waiting for their results after a series of deadlines were missed.
The committee said "ministers' fingerprints" were on the crisis.
It also said government agencies should stand up to ministers more.
The failure of the Sats marking system in 2008 became a major scandal, leading to the removal of the contractor ETS Europe.
This was followed by an independent inquiry by Lord Sutherland and the acrimonious departure of Dr Ken Boston, head of exams watchdog, the Qualifications and Curriculum Authority (QCA).
The Key Stage 3 national curriculum tests taken by 14-year-olds were also scrapped.
The cross-party Children, Schools and Families committee said in a report that micro-management by government officials contributed to confusion, blurring the lines of responsibility.
The committee said exam bodies needed more independence from government to make key decisions.
Barry Sheerman wants Ofqual to be "absolutely independent... free to speak its own mind"
The report said: "We believe that DCSF has involved itself too much in the detail of delivery, placing undue constraints on the executive decision-making abilities of its agency, QCA.
"We recommend that the leadership of government agencies should be more prepared to stand up to the government when it considers that directions from the government to the agency are unreasonable or incapable of performance."
The MPs raised concerns about the role of observers from the Department for Children, Schools and Families, who sit in on meetings of public bodies, saying they exerted "undue influence".
The committee said the role of such observers should be clarified and safeguarded to prevent what it called "inappropriate interference".
Chairman of the committee, Barry Sheerman, said: "There is no question that events in the summer of 2008 were incredibly disruptive for a significant minority of pupils, parents and teachers.
"We have identified significant flaws in the department's management of its relationship with QCA.
"We urge the government to do everything possible now to ensure that this summer the same mistakes are not repeated.
We are not saying Ed Balls and Jim Knight were manipulating everything...they weren't doing that, but at the same time their fingerprints are on part of this
Barry Sheerman, Chairman, Schools Select Committee
"We intend to monitor closely the work of Ofqual to make certain its independence as a regulator is beyond doubt."
Mr Sheerman told the BBC: "This is a nuanced report. We are not saying Ed Balls (Schools Secretary) and Jim Knight the schools minister were manipulating everything.
"They weren't doing that, but at the same time their fingerprints are on part of this in the sense that the department has observers at all these meetings.
"There is no doubt there was quite a close relationship between the department and what was happening in the QCA."
The committee's report said it was "regrettable" that ETS, the American company behind the doomed test delivery, withdrew from the UK and "chose not to engage" with Lord Sutherland's inquiry into the fiasco.
And it welcomed the abolition of the Key Stage 3 tests.
Schools Minister Vernon Coaker said the test contractor ETS and the QCA were to blame for the problems last year.
"It's now time to draw a line under 2008 and get on with the important job of making sure our assessment system is the best it can possibly be, so that both pupils and parents can continue to get the information that we know they value," he said.
Liberal Democrat spokesman on schools, David Laws, said: "This report discredits Ed Balls' previous attempts to shift all of the blame for the marking fiasco on to the QCA.
"It's clear that his department played a key role in the failure to deliver the test results on time.
"It is outrageous that so-called observers were influencing a public body in this way."
Mr Laws added that England needed a fully independent "Education Standards Authority, with real powers to stand-up to the government".
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