Monkeypox is continuing to spread in the UK, with current efforts insufficient to curb the outbreak, experts have warned as a whistleblower claimed there were serious flaws in the support given to those who think they have been exposed.

According to the UK Health Security Agency (UKHSA), there have been 1,552 confirmed cases of monkeypox in the UK related to the outbreak as of 7 July.

While anyone can catch the virus as it is spread through close or intimate contact, the majority of cases so far have been among gay and bisexual men, and men who have sex with men (MSM). Within England, the majority of cases have been in London.

There is little sign of infections fizzling out, with the latest estimates from UKHSA suggesting case numbers are doubling every 15 days.

“[There is] no evidence that current strategies are likely to bring this to an end anytime soon,” said Paul Hunter, a professor in medicine at the University of East Anglia, although he noted that while total case numbers were continuing to rise, the rate of new infections may have plateaued.

The concerns came as a whistleblower working on a UKHSA monkeypox inquiries line said it had numerous issues, including offering little support for people who are not confirmed contacts of cases – ie somebody whose name has been provided to contact tracers by a person with monkeypox.

The Guardian has seen scripts that show even if someone calls because they are worried they may have had a contact with a confirmed case, they are told their risk is very low if they have not been formally identified as a contact. The whistleblower said that made little sense when a caller has said a sexual partner has monkeypox symptoms.

In addition, the whistleblower said call handlers were not allowed to suggest callers contact a sexual health clinic unless sexual health was brought up by the caller, They added that some clinics had turned off their phone lines.

The UKHSA has rejected the claims, saying the phone line is an additional service to provide non-clinical advice to members of the public.

Dr William Welfare, the agency’s incident director, said specialist public health teams were rapidly following up all cases to limit transmission, with contacts assessed as high risk offered vaccination.

“Contact tracing has often relied on people sharing contacts for a high number of sexual contacts, so can inevitably be difficult when also taking into account confidentiality. We have rapidly implemented a high-quality public health operation with sexual health services to investigate and control monkeypox, and to support those affected,” Welfare said.

“Monkeypox is predominantly being spread by very close contact, most prominently through relatively closed sexual networks, and has not been found routinely in the wider population. The prevalence of infection overall in the UK and therefore the risk to the general public currently remains low.”

Vaccination involves a smallpox jab that also offers protection against monkeypox. The UKHSA recently announced it would broaden eligibility for vaccination to include some gay and bisexual men at higher risk of exposure to the virus even if they were not a confirmed close contact of a case.

The UKHSA confirmed there was a ready supply of vaccine, with almost 30,000 doses procured, but said the NHS had yet to announce plans for the rollout of the jab.

A NHS spokesperson, said: “The NHS is working with local partners to identify and invite those who are eligible for a vaccination to come forward, and over the coming weeks will rapidly grow the number of clinics to make it as quick and convenient as possible to get vaccinated.

“Following UKHSA advice, the NHS will continue to prioritise vaccination for those at greater risk, including healthcare workers in specialist roles and clinics where exposure to Monkeypox is highest.”

But Hunter said an even broader approach may be needed. “I think wider vaccination of high-risk MSM – people who have frequent multiple contacts – and maybe female sex workers are the way forward,” he said. “We may not have enough vaccine to do this but I think there could be a case to offer vaccine to everyone attending an STD [sexually transmitted diseases] clinic.”