An ambulance trust has hit back over an MP’s claims that delays over the festive period cost 20 people their lives.

Last month MP Clive Lewis told the Commons that East of England Ambulance Service NHS Trust failed to move into its highest state of emergency over 12 days in December.

He said a whistleblower had told him the decision was not taken until December 31, which could have resulted in 20 people dying.

However, a spokesperson for the ambulance service has since told The Observer that the trust is investigating 22 “serious incidents” where 12 people died.

They added that the whistleblower was not being investigated.

The spokesperson said: “There are 22 serious incidents, out of which 12 sadly died.

“The nature of serious incidents means that we thoroughly investigate, both for the patients and their families and so that we learn lessons.

“We are investigating an information governance breach, not the whistleblower. We urge people to continue to speak up so that we can improve.”

The trust received 4,200 calls on Boxing Day and snowy conditions the following day resulted in “another day of busy calls”.

Kevin Brown, director of service delivery for the service, said at the time: “The health system is experiencing this spike with us, and every trust is doing everything possible to work together for good patient outcomes.

“We will always prioritise patients with life-threatening conditions above other calls and that calling 999 should be for these sorts of emergencies only.”

Mr Lewis, who represents Norwich South, said on Wednesday, January 17, that senior managers wanted to move East of England Ambulance Service Trust to so-called REAP 4 on December 19.

The Resource Escalation Action Plan (REAP) aims to maintain an effective and safe response for patients.

He asked speaker John Bercow about how to get a response from the Health Secretary.

Mr Bercow responded that Mr Lewis should table questions to the Health Secretary and consult colleagues on the Labour frontbench.

The claims came just days before the medical director at the trust Dr Mark Patten announced he was resigning.

Dr Tom Davis took over his role at the beginning of this month.