Liz Truss is to introduce a draft law that will seek to ban biological males from entering single-sex spaces and prevent children from attempting to change their gender.

The former prime minister, who spent only 49 days in office, was among 20 MPs selected to bring forward a Private Member’s Bill – a process that allows backbenchers to introduce a new law separate from the Government’s legislative agenda.

Aides said the right-wing Conservative will use the opportunity this week to propose a Bill that would look to ensure single-sex spaces are protected in law by preventing transgender women, who have transitioned from being a male, from accessing areas like female toilets and changing rooms.

The draft legislation will also aim to prevent under-18s from accessing hormone therapy and block the state from recognising social transitioning by those under the legal age of adulthood, a source close to the former Tory leader said.

They said Ms Truss feels there need to be stronger protections in law to prevent under-18s from “making irreversible decisions about their bodies which they might come to regret”.

Ms Truss was 18th among the names revealed in the ballot last month, meaning there is no guarantee that her Bill will be debated in the Commons.

Normally, only the first seven balloted Bills will have time to be included in a day’s debate and therefore have the highest chance of becoming law.

A source close to Ms Truss told the PA news agency: “In her time as minister for women and equalities, Liz successfully blocked dangerous plans to allow gender self-ID.

“It has become increasingly clear there is a need for the law to better protect children and teenagers from making irreversible decisions about their bodies which they might come to regret.

“The law also needs to be amended in order to make it clear that biological males should be legally excluded from having access to single-sex spaces designated for women, including toilets, changing rooms, refuges and prisons.

“Liz decided to put forward these proposals after considering the amount of correspondence she receives on these issues and taking soundings from her South West Norfolk constituents.

“These are not party political issues and she hopes to bring together a broad cross-party alliance in support of her Bill.”

The contents of the Bill, news of which was first reported by the Mail On Sunday, will be formally presented to the Commons on Wednesday, along with a list of its MP backers.

Julie Elliott, Labour MP for Sunderland Central, came first in the ballot and will have top priority to bring forward a legislative proposal.

A UK Government spokeswoman said: “This Government is clear of the fundamental importance of biological sex.

“The Equality Act already allows single-sex spaces to be restricted on the basis of sex where that is justified, and the EHRC (Equality and Human Rights Commission) has published extensive guidance to support providers.

“NHS England is also making significant improvements to children’s gender identity services to protect children, including consulting on measures to severely restrict, the prescribing of puberty blockers to children aged 16 and under.

“As set out in the Cass Review’s interim report, social transition is not a neutral act, so any decision to social transition should be in the best interests of the individual.”