By Michael Holden

LONDON (Reuters) -British prosecutors said on Wednesday they were considering bringing further charges against nurse Lucy Letby, already convicted of murdering seven babies, over allegations relating to deaths and other incidents at hospitals where she worked.

Letby, 35, is already serving life in jail and will never be released after being found guilty of attacking the newborns and attempting to kill eight more at the neonatal unit of the Countess of Chester Hospital in northern England between June 2015 and June 2016.

Letby, Britain's worst serial child killer of modern times, has maintained her innocence throughout but has been refused permission to appeal. Her lawyers are seeking to have the case reviewed, saying there are serious doubts over whether she was guilty of any crimes.

However, following her convictions, police said they were examining whether she had committed at further crimes while at the Chester hospital, or at the unit where she had previously worked, and the Crown Prosecution Service said it was now examining the evidence.

"We can confirm that we have received a full file of evidence from Cheshire Constabulary asking us to consider further allegations in relation to deaths and non-fatal collapses of babies at the Countess of Chester Hospital and Liverpool Women’s Hospital," a CPS spokesperson said.

"We will now carefully consider the evidence to determine whether any further criminal charges should be brought."

It said a referral by police did not mean charges would follow.

Since Letby was jailed, some lawmakers and medical experts have publicly challenged the prosecution evidence that was used to find her guilty, with some experts querying whether any babies had actually been murdered at all.

The Criminal Cases Review Commission, which examines potential miscarriages of justice, is currently considering an application from Letby's legal team.

"The concerns many have raised will not go away, and we will continue to publicly discuss them," her lawyer Mark McDonald said on Tuesday.

Those comments came after detectives said they had arrested three unnamed senior members of the hospital's leadership team as part of their investigation into individuals and the Chester hospital itself.

"Both the corporate manslaughter and gross negligence manslaughter elements of the investigation are continuing and there are no set timescales for these," said Detective Superintendent Paul Hughes, who is leading the investigation.

The CPS said it had not yet been asked to consider any charges in relation to the investigation into the staff or the hospital itself.

(Reporting by Michael Holden and Catarina Demony; editing by William James and Alex Richardson)