Jeremy Hunt will update MPs on the UK's ability to cope with Ebola as a British nurse remains in a critical condition with the virus.

The Health Secretary will make a statement in the Commons to MPs returning to Westminster following the Christmas break as Save the Children promised that a review into how nurse Pauline Cafferkey contracted the disease will leave "no stone unturned".

The Royal Free Hospital in north London said Mrs Cafferkey's condition had deteriorated over the past few days while she was being treated with an experimental antiviral drug.

The Scottish public health nurse had volunteered with Save the Children at the Ebola Treatment Centre in Kerry Town, Sierra Leone, before returning to the UK, and the charity said today that it was urgently reviewing its protocols.

Charity spokesman Rob MacGillivray told the BBC he hoped to discover whether Mrs Cafferkey had contracted the virus while at the treatment centre or in the community.

He said: "We have a review on at the moment - we are constantly reviewing our protocols and procedures to ensure staff working in Kerry Town centre take all measures possible to prevent themselves becoming infected with Ebola.

"And because of this very serious event we have put in an extraordinary review to ensure that we do everything we can and leave no stone unturned to, as far as possible, identify the source of this infection.

"Everybody is exposed to a certain amount of risk working in Sierra Leone at the moment but we will certainly be focusing on how the personal protection equipment was used, how it was put on and, more importantly, how it was taken off, the kinds of contact people have had perhaps in Kerry Town centre and perhaps outside, so it it will be a very full and thorough review."

Mr MacGillivray added that he was "confident" in the protocols the charity had in place and said the results of the review would be published once completed.

Mrs Cafferkey, who works at Blantyre Health Centre in South Lanarkshire, was part of a 30-strong team of medical volunteers deployed to Sierra Leone by the UK Government in November and had been there for three weeks before returning home on rotation for a break, the charity boss added.

Prime Minister David Cameron said Ebola is the "uppermost thing" on his mind following news of Mrs Cafferkey's condition.

He told BBC1's Andrew Marr Show: "It's (Ebola) certainly the thing uppermost in my mind today with Pauline Cafferkey in hospital, and all of us are thinking of her and her family.

"And also how incredibly brave these people are, not only doctors and nurses from our NHS but also people from our armed forces who have been working in West Africa in very difficult conditions."

Mrs Cafferkey first raised concerns about her temperature when she returned to Heathrow Airport last Sunday, but despite undergoing seven temperature checks she was given the all-clear to fly to Glasgow, where she lives.

The following morning she was diagnosed with Ebola and placed in isolation at Gartnavel Hospital campus in Glasgow before being flown south.

The PM said he was listening to medical experts about whether a system of quarantine should be put in place for returning health workers.

Asked whether airport screening is failing, he said: "Her temperature was taken several times but then she was allowed to go on and travel to Scotland and what I have said very clearly is we should have a precautionary principle in place.

"If you are still in doubt, if there's uncertainty, there's proper arrangements for you to go to the Northwick Park Hospital in Middlesex to be observed and to have further tests there before going further.

"That is happening already, I am absolutely clear about that.

"If we need to change further, if the Chief Medical Officer says we need a system of quarantine or anything like that, then we should put that in place.

"But it is important to listen to the medical experts and then make the decision."

The Government's Chief Medical Officer, Dame Sally Davies, acknowledged last week that questions had been raised about the airport screening procedure for Ebola.

The Royal Free Hospital said on Saturday: "The Royal Free London NHS Foundation Trust is sorry to announce that the condition of Pauline Cafferkey has gradually deteriorated over the past two days and is now critical."

Her sudden change in condition came after her doctor described her as sitting up, eating, drinking and communicating with her family on New Year's Day.

Dr Michael Jacobs warned that she faced a "critical" few days while she is treated with convalescent plasma taken from the blood of an Ebola survivor and an experimental antiviral drug which is "not proven to work".

She is the second Briton to test positive and the first to do so on UK soil after nurse William Pooley, 29, contracted Ebola while volunteering in Sierra Leone in August before getting the all-clear following treatment at the Royal Free Hospital.

The Royal Free, where Mrs Cafferkey has been treated since Tuesday, was unable to obtain ZMapp, the drug used to treat Mr Pooley, because "there is none in the world at the moment".

The hospital has insisted there is "no danger" to staff or patients and it is "open for business as normal" while the 39-year-old is treated in an isolation unit.

In a statement it said: "The Royal Free London is currently treating a patient for the Ebola virus in a high-level isolation unit.

"There is no danger to patients or staff during this time.

"The Royal Free Hospital is open for business as usual, with in-patient, out-patient and emergency care continuing as normal."

Public Health England confirmed on Friday that all UK-based passengers and crew on board the two flights taken by the nurse from Morocco and London were contacted by medical authorities and given advice.

Save the Children said it may never be possible to be 100% sure how Pauline Cafferkey was infected.

The statement from the charity said: "Save the Children has been conducting a review since Pauline Cafferkey was confirmed as Ebola positive.

"The Serious Event Review (SER) is looking at how the patient might have contracted Ebola by reviewing training, safety protocols, how protective equipment is used, and working practices.

"The findings of the review will be considered by a panel including independent health experts, which will support Save the Children and make recommendations for any actions if necessary.

"The early findings of the review will be made available by Save the Children as soon as possible.

"As with other Ebola infections in health facilities, it may never be possible to be 100% sure how the patient was infected.

"The work of these brave health workers is never risk-free, but we are committed to doing everything possible to learn what happened and, if necessary, to make changes to our protocols and practice. Staff safety is our number one priority and our thoughts are with Pauline and her family at this very difficult time."