Scottish adults and children will be allowed to change their gender so that legally they are neither male nor female, under controversial plans to overhaul the law unveiled by SNP ministers.

The Scottish Government unveiled plans to create a “non-binary” gender for people who do not identify as a man or woman and to make it legal to “self-declare” which gender they want to be.

This means that Scots could change their legal status to male, female or non-binary without any medical diagnosis or treatment, and potentially switch more than once.

A consultation paper on the plans stated that ministers favour setting a minimum age of 16 for people wanting to change their gender, although one of the options under consideration would mean pre-pubescent children could also make an application.

The document noted that the law around parentage and marriage must be changed to “clearly include non-binary people”. The criminal law may also have to be overhauled “to ensure that any remaining gender specific offences can be committed by people of all legal sexes.”

However, it noted there could be “financial implications” for the public purse as NHS Scotland tries to put all hospital patients in single-sex wards, toilets in public buildings are either male or female and the Scottish Prison Service may have to spend up to £10.7 million for a unit that could accommodate up to 30 non-binary people.