The American company responsible for failing to deliver millions of school exam results on time this summer has laid much of the blame for the delays at the Government’s door.

Dr Philip Tabbiner, from ETS, was hauled before the Children, Schools and Families Select Committee to answer for the way the company handled the marking of millions of national curriculum tests, which delayed results by more than a month.

He told the group of MPs there had been "technical and operational problems" - mainly owing to changes to its contract – which had caused the delays. But he apologised for the hold-up.

The company was engaged by the Government’s National Assessment Agency (NAA) to deliver the tests but Dr Tabbiner said the NAA had insisted on late changes to the way ETS trained markers. This he said had created considerable problems.

He said (NAA) shared “significant responsibility for the delivery failure” and claimed the agency had dramatically changed the terms of their contract after it had been agreed.

Dr Tabbinger, the senior vice-president of ETS, said: “These issues were exacerbated by programme changes required by the NAA [and] long delays by NAA on key project decisions.”

He said that extra requirements added by the NAA after the contract had been signed also added to the problems.

MPs heard that ETS had not shied away from taking responsibility for the delays, and acknowledged that markers had been allocated the wrong scripts and were unable to view their allocated papers online.

Dr Rabbiner was giving the company's first full public account of what went wrong.

ETS had not been able to do this until now, he said, because of contractual agreements.

ETS Europe had a five-year £156 million contract to carry out marking of the tests for 11 to 14-year-olds, but it was dissolved in August after a summer of delays and complaints from markers and teachers.

The results of the Key Stage 2 and 3 SATs tests were delayed by more than a month in what has been roundly criticised as a shambles.

Kathleen Tattersall, chairwoman of the exam regulator, Ofqual, and Isabel Nisbet, chief executive of the watchdog, are also giving evidence to the committee. They will be asked to explain how a repeat of this year’s problems will be avoided in marking the 2009 tests.

ETS has to pay back £19.5 million to the Qualifications Curriculum Authority who employed them in February last year, and owe another £4.6 million for the cancellation of invoices and charges. They were originally paid £35 million to carry out the marking this year.

Barry Sheerman, chairman of the committee said the delays had caused “a great deal of inconvenience for everyone involved”.

He said: “A lot of people have said it’s all the fault of this American firm, [that] they didn’t understand the scale of the task, but we haven’t heard from them to give their opinions.”

“We want to get to the bottom of what’s happened, and I don’t think we have got to the bottom of it yet. This is our opportunity to do so.

ETS was widely criticised for its handling of this year’s tests, which saw thousands of schoolchildren break up for the summer holidays without knowing their results.

The company apologised to pupils, parents and schools for the delays, but insisted there was no evidence of problems with the quality of marking, a sentiment also expressed by Ofqual.

The Schools Secretary Ed Balls has signalled that next year’s tests could be the last, saying that the current system is “not set in stone” and may be replaced by assessments tailored to each child’s ability level.

An independent inquiry into the delays, led by Lord Sutherland, is due to report back in the autumn.

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