Child welfare campaigners, politicians and lawyers have warned of the potential for confusion following a move in the House of Lords to tighten the law on smacking.

Last night peers passed by 226 to 91 an amendment to the Children Act that would leave parents who deliver anything more than a light smack facing jail.

While lawyers questioned whether parents would know what degree of force was permissible, campaigners who had been seeking a total ban said the result was "shameful".

Attorney general Lord Goldsmith had warned that a total ban risked "criminalising parents".

But the Mail warns that parents who deliver a slap that causes the skin to redden could face prosecution.

Some MPs are to seek a total ban when the legislation returns to the Commons.