The Government has moved to deny last week's press reports that baseline assessment will be used to group infant pupils by ability.
In a rocky start to his career as schools minister, Charles Clarke appeared to favour the idea of using the new tests in order to place four and five-year-olds in academic sets.
"I have sympathy with more setting in primary schools," he told journalists at the launch of the compulsory assessments, which are designed to help teachers diagnose the strengths and weaknesses of their new intake.
"Teachers should use all the evidence at their disposal, of which these tests are a part, but only a small part."
But clearly rattled at the media coverage, which included angry comment from teachers' leaders and a hostile front-page piece in the Daily Express,Mr Clarke has written to national newspapers, including the TES: "I made it clear I saw no direct relationship between baseline assessment and setting or streaming and that I did not believe the assessments were the vehicle to achieve more setting."
He attempts to reassure teachers that the tests will be an "invaluable" tool and adds: "In every case I know that these assessments will simply be building on the foundations of existing good practice."
Ministers had already written to around 1 million parents urging them not to try to coach their children for the assessments as it might "hide the real situation".
However, the advice leaflets, which were distributed through Britain's 21,000 primary schools, list seven ways in which parents can help support their children's learning. These include talking about books, encouraging children to concentrate and using numbers in everyday situations.
"It is important that teachers and parents understand directly, openly and honestly what a child's capabilities are," said Mr Clarke.
Under the new system, 600,000 reception pupils will be assessed for reading, writing, speaking, maths and concentration within seven weeks of starting school. Teachers will be expected to discuss their results with parents.