Nancy pelosi warned that a covid-19 vaccine should not be authorised for use in the us based on data from british trials, amid fears that the trump administration is planning to rush out an inoculation before election day.

The democratic speaker of the house of representatives on friday cast doubt on the british system for testing and approving medicines, further politicising the race to develop a vaccine for covid-19.

We need to be very careful about what happens in the uk. we have very stringent rules in terms of the food and drug administration here, about the number of clinical trials, the timing, the number of people and all the rest, ms pelosi told reporters in washington.

She added: my concern is that the uks system for that kind of judgment is not on a par with ours in the united states. so if [prime minister] boris johnson decides he is going to approve a drug and this president embraces that, that is a concern that i have.

In august, the financial times reported that the trump administration was considering bypassing normal us regulatory standards to fast-track a vaccine being developed by astrazeneca, a uk-based drugmaker, for use in america ahead of the election.

The hunt for a coronavirus vaccine has become one of the most hotly-contested topics during the us presidential campaign. president donald trump has said he would like to have one before next months election, even though his own administrations top health officials say it is not likely to be released until later in the year.

Democrats have warned that any vaccine approved by mr trumps administration might not be safe.

Speaking during this weeks televised vice-presidential debate, kamala harris, the democratic candidate, said: if the doctors tell us that we should take it, ill be the first in line to take it, absolutely. but if donald trump tells us that we should take it, im not taking it.

The fda has in recent days published a set of approval guidelines that would make it difficult for a developer to secure an authorisation before november 3, especially given that us trials of the astrazeneca candidate have been paused in the us due to safety concerns.

Trump officials are exploring speeding up the process by granting emergency use authorisation to astrazeneca based on the results from a relatively small uk study if it is successful, the ft reported in august.

The astrazeneca study has enrolled 10,000 volunteers, whereas the us governments scientific agencies have said that a vaccine would need to be studied in 30,000 people to pass the threshold for authorisation.

Ms pelosis comments appeared to be warning against exactly such a scenario, although the democrats have no real power to stop it happening. neither the fda nor the british government immediately responded to a request to comment.