Teachers are being asked not to share the contents of a national primary test that has been accidentally published online in advance of most schools sitting it.

The mistake emerged this week as the first schools to take this year’s key stage one spelling punctuation and grammar test realised that pupils had already seen the questions.

Tonight the Department for Education admitted that the test had been published in error by its testing agency and said that an inquiry had begun.

But a spokesman told TES that it was too late to change the test that has yet to be sat by thousands of primaries in England. He appealed for teachers not share the contents of the test, which form part of teacher assessments for seven-year-olds.

“If it emerges that the children have seen this before they should take that into account when they are marking the test,” he added.

The test was uploaded in error to the Standards and Testing Agency website as part of the exemplification materials available to schools, earlier this month.

The mistake emerged this week as a batch of around 700 primaries began to pilot the test this week and realised the questions were familiar.The error has now been shared on social media, where it has been described as an “omnishambles”.

A DfE spokesperson said: “This is clearly a serious error and we have launched an immediate investigation to understand how it happened. The material has been removed from our website. Fortunately, this is a key stage 1 test which is provided to schools to support Teacher Assessment judgments.

“The data used to judge the performance of schools and the progress children are making at key stage 1 are teacher assessment judgements. The results of these tests are not collected. Nonetheless it is deeply regrettable that it has happened.

“We ask that if anyone has seen the material, they do not share it further so that the test remains helpful for those teachers who have not yet used it with their pupils.”