More than 500 parents and carers were arrested on suspicion of neglect for leaving a child at home alone in 2015.
The youngest child left alone was a six-week-old baby, the BBC learned through a Freedom of Information (FOI) request, according to PA.
The oldest child left alone deemed at risk was 15 years old, but the majority of children were under 10.
Although 510 people were arrested on suspicion of neglect, there are fears the numbers could be higher, as only 28 out of 43 police forces responded to the FOI.
There are no laws about the age a child can be left alone, but police can take action if they deem a child to be "at risk".
The National Society for the Prevention of Cruelty to Children (NSPCC) has guidance on its website, stating that babies and toddlers should never be left alone and under-16s should not be left alone overnight.
The advice states: "Children under the age of 12 are rarely mature enough to cope in an emergency and should not be left at home alone for a long period of time."
However the NSPCC said it received 2,500 calls from adults worried about children left alone last year, many in the summer holidays.
Former MP John Hemming is now campaigning for clearer advice for parents.
Mr Hemming, a Liberal Democrat MP for 10 years until 2015, said he was worried about the lack of clarity in the law.
He wrote on his blog: "The Government claim that parents are allowed to decide whether their child is mature enough to be left alone. That, however, is not true.
"What happens is that either the police or local authority social workers decide whether in their opinion the parents have neglected their child."
He added: "We need to consider what is optimal, what is ill-advised and what should be criminal or require action from the local authority."
To read the NSPCC's advice on leaving children home alone, visit their website.
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