A new report out tomorrow reveals that many of the under sevens, under the age of criminal responsibility, were searched by Strathclyde Police without grounds of suspicion.
The findings show that some stop-and-searches for the whole of the Strathclyde population had a success rate of one to 2%.
Tam Baillie, Scotland's Commissioner for Children and Young People, said he was "extremely concerned" at stop and search tactics being used on young children.
Stop and search is a tactic used by police to catch criminals in possession of firearms, knives, drugs and stolen goods. The policy was massively stepped up when House was chief constable of Strathclyde Police and its use has been rolled out by the new single force to all parts of the country.
Two types of search exist: statutory searches, which can only be carried out if officers have reasonable grounds of suspicion; and the more controversial non-statutory stops, which are based on consent. Scotland is the only part of the UK that permits non-statutory searches. An investigation into the single force's use of stop and search by the Scottish Police Authority (SPA) last week found that 229 under nines had been searched by the single force.
However, a new report by Edinburgh University academic Kath Murray has revealed that searches by House's old force were carried out on even younger children.
Focusing on Strathclyde police, she found that more than 1.2 million searches were recorded on the Strathclyde population from 2005 to 2010. House took over as chief constable of the force in 2007.
The report reveals that 893 searches were carried out on children aged seven and younger. The criminal age of responsibility is eight. Children's charities are pushing for the age of criminal responsibility to be raised to 12.
Of the 893 searches on seven and unders, which included children in primary two, 45% were "non-statutory" and based on the child's consent. Murray, who is based at the Scottish Centre for Crime and Justice Research, noted: "Non-statutory stop searches undertaken on children this young cannot be based on informed consent."
Murray's report casts doubt on the effectiveness of Strathclyde's heavy use of non-statutory searches.
Of the 1.2 million searches, more than 75% were consensual. But only 5.2% of the consensual searches resulted in a detection. Senior police officers have defended stop and search on the grounds that it is "intelligence led", but only 1% of consensual searches detected an offensive weapon, while the figure for drugs was 2%.
Murray said: "The analysis highlights a range of concerns, specifically that non-statutory stop and search is uncodified, unregulated, falls disproportionately on young people and is unlikely to result in a detection."
Scottish LibDem MSP Alison McInnes said: "How can you expect a seven-year-old to give informed consent to a police search? I continue to press the Scottish Government to change the law to put all police searches on a full legal basis, to rein back the Strathclyde approach which has got out of hand."
Assistant Chief Constable Wayne Mawson said: "This report is historic looking at legacy police forces and does not take into consideration the many changes already carried out by Police Scotland and the report on stop and search by the Scottish Police Authority.
"Young children are very rarely stopped and searched but when they are it is usually for their own welfare or child protection issues."