LONDON (REUTERS) - Two British doctors who have been exposed to Covid-19 patients have launched a legal challenge against the government over what they say is a lack of protective kit and unclear guidance on when and how it should be used.

The issue of personal protective equipment (PPE) for doctors and nurses on the front line of the new coronavirus outbreak is one that has dogged the government, with persistent reports that there is not enough kit and that some of it is not good enough.

Lawyers for the two doctors, a husband and wife who are expecting a child, wrote to Health Minister Matt Hancock on Thursday (April 23) to demand an urgent review of the official PPE guidance and to complain about how the kit was being sourced.

"It is the government's duty to protect its healthcare workers, and there is great anxiety amongst staff with regards to safety protocols that seem to change without rhyme or reason," said the doctors, Meenal Viz and Nishant Joshi, in a statement issued by their law firm Bindmans.

Viz is a clinical fellow in medicine and Joshi is a trainee general practitioner. Both are employed by the state-run National Health Service (NHS). So far, 69 people working for the NHS have died of Covid-19.

The two doctors say the British PPE guidance is not in line with World Health Organisation standards, exposes healthcare workers to a greater risk of contracting the virus, is unclear and has resulted in inconsistent practices.

They want the guidance be amended to make it consistent with WHO standards, to explain the risks associated with the use of different types of PPE, and to clarify the right of staff to refuse to work where they consider PPE to be inadequate.

The letter is a precursor step to going to court to seek a judicial review of the guidance.

The health ministry could not be reached by phone and did not immediately respond to an email seeking comment.

The doctors took particular issue with a change to the guidance last week, to add that plastic aprons could be used instead of protective gowns in some situations. This caused widespread dismay among doctors.

The Public Health England government agency says the new guidelines comply with WHO advice, which states that while aprons are an alternative to gowns, they "should be avoided when performing aerosol-generating procedures", the riskiest work frontline doctors do.

The new British guidance specifically says aprons can be used even for such high-risk procedures.