Peers have voted to tighten the rules on smacking children.

In a vote on Monday evening, they backed an amendment to the Children Bill that would allow mild smacks that fall short of causing actual bodily harm, while preventing more serious punishment.

A bid to introduce a total ban on smacking failed after the government refused to back it.

Ahead of the vote, Downing Street reaffirmed its opposition to a total ban on smacking.

Number 10 said a "balance" should be struck between "parents' right to discipline and protecting the child".

The peers backed an amendment brought forward by Lord Lester of Herne Hill which proposes a tightening of the law.

His compromise amendment would continue to allow parents to use physical force, but they would have to stop short of causing physical or mental harm.

It would also outlaw hitting any child with an implement, such as a cane.

No ban

The prime minister's official spokesman said the government was allowing a free vote on Lord Lester's amendment, which it feels does not go as far as a total ban.

"The government's position remains that we are opposed to a ban on smacking and anything that could be legally interpreted as a total ban," he said.

Asked why a free vote on the amendment was being allowed, the spokesman added "there is a difference between an outright ban and what Lord Lester is proposing".

He argued that parents would be able to tell the difference between discipline and abuse.

Ministers have been wary of supporting a total ban and are keen to avoid accusations of adopting a "nanny-state" approach.

Children Bill

The smacking vote forms part of the Children Bill, which aims to prevent a repeat of tragedies such as the death of Victoria Climbie.

The eight year old died after suffering horrific abuse at the hands of adults acting as her adoptive parents.

The government believes the tragedy wasn't down to a deficiency in the law but was caused by failures in social service monitoring of the girl's case.

However, campaigners are not satisfied by incremental reform.

"We need to move into the 21st Century on this issue and leave archaic legislation such as this where it belongs - back in the Victorian era," said Mary Marsh, director of the National Society for the Prevention of Cruelty to Children.