In a joint letter, five charities dealing with sexual health and transmission of blood-borne viruses such as HIV and hepatitis C said the recently announced delay in legislative change to the Gender Recognition Act (GRA) means "ongoing harm" to gender-diverse people.
The Scottish Government had planned to change legislation to remove the need for trans people to provide evidence - including medical records - that they have lived in their chosen gender for at least two years.
The Government announced last month reforms would be delayed for a further consultation before a draft Bill is introduced at Holyrood before the end of the year, despite holding a 16-week consultation last year.
More than 15,500 responses were received to the 2018 consultation but less than half were from Scotland. Of those Scottish responses, 65 per cent were in favour of reform.
Waverley Care, Scottish Drugs Forum, Terrence Higgins Trust, HIV Scotland, and LGBT Health and Wellbeing have now written a joint letter to Social Security and Older People Secretary Shirley-Anne Somerville, urging no delay to the draft Bill consultation.
The letter states: "While the proposed system is not in place, trans and non-binary people continue to be subjected to intrusive and harmful medical requirements to gain basic recognition of their gender identity.
"We urge the Scottish Government to consider the ongoing harm caused to people who are gender diverse in engaging with the current system.
"Moreover, we are concerned that a second consultation phase invites continued societal discourse on the legitimacy of trans people's experiences and adds another layer of harm to their health and wellbeing."
Trans and non-binary people are "disproportionately affected" by poor sexual health, it adds, and worldwide trans women are 49 times more likely to be HIV positive than the general population.
The letter continues: "We know from evidence that people who are marginalised in society face barriers to accessing sexual health services, including fear and stigma.
"The trans people we work with tell us that fear of misgendering and a lack of compassionate support prevents them from accessing basic sexual health services, including contraception and STI prevention.
"GRA reform is a key step in addressing the marginalisation of trans and non-binary communities, by allowing people to more easily gain legal recognition of their gender identity.
"By reducing the marginalisation trans and non-binary people face, GRA reform would enable better access to sexual health services and assist our organisations' work to reduce HIV transmissions."
The charities also urge the Government to "consider the inclusion of people who are non-binary in the development of a system of self-determination".
Announcing the delay last month, Ms Somerville said the Scottish Government is committed to reforming the GRA, and any new proposals are still likely to remove the need for applicants to provide medical evidence, but "the current requirements will be replaced by an alternative statutory process".
A Scottish Government spokesman said: "Everyone in Scotland has fair and equal opportunity to access the best possible healthcare and support, whatever their needs.
"As the Cabinet Secretary for Social Security and Older People said in her Parliamentary statement in June, the Scottish Government will have a full public consultation later this year on a draft Bill."