By Justin Parkinson BBC News Online education staff at the NAHT conference

Charles Kennedy was speaking to head teachers

They should be allowed to develop their "own initiative", he told the National Association of Head Teachers' conference in Cardiff.

Mr Kennedy said it was still important to create a national profile of seven year olds' achievements. But he said this should be compiled by "random sampling", so they were "unaware" they were being tested.

Mr Kennedy's comments come amid concern about the effects of tests on seven year olds in England. They are not taken at this age elsewhere in the UK.

Some critics, including the National Union of Teachers, say they might even be "psychologically damaging".

'Profiling'

Mr Kennedy said that, if his party were elected: "Random sampling on core skills will be used to create a snapshot of the year group across the country.

"Profiling would prove beneficial for pupils, parents and teachers alike. Pupils would be unaware that they were being tested, thus removing the considerable stress involved."

Critics say English pupils are over-tested

He added: "Internal assessment would then be used to allow parents and teachers to assess the progress of parents against national norms."

Mr Kennedy said the Lib Dems would also create a national Early Years Centres network.

These would help end the "false divide between when care ends and education starts".

He told the conference: "One of my real concerns about the current government's approach to education is that it regards the whole [education] process as utilitarian."

It was important to "create a thirst for learning".

Mr Kennedy said it was necessary to have appropriately trained staff looking after children throughout their school lives.

He said: "We want to see smiles on the faces of our children at the end of the school day when they are aged seven; but the smiles should still be there at 14."