Health bosses have held an urgent meeting into patient safety at an ambulance trust following a string of incidents, including one in which a man was found dead in freezing conditions.
Tony Barnard was found outside his former Suffolk home, 18 hours after authorities were told he was at risk.
His brother has called on the police and East of England Ambulance Service (EEAS) to provide answers.
NHS England said an "action plan" was agreed at the "risk summit" on Tuesday.
The meeting was held by NHS England and NHS Improvement to look at how EEAS handles patients.
Concerns about patient safety have already been raised with the Prime Minister after a whistleblower claimed a number of people, including Mr Barnard, had died while waiting for ambulances.
The 57-year-old was found dead in freezing conditions by neighbours outside the home in Lowestoft he had been evicted from. Both the ambulance service and police had been alerted to concerns for his safety the previous day.
EEAS confirmed that 40 potential serious incidents were reported by its staff over the Christmas period.
And Norwich South MP Clive Lewis told the Commons 20 people died after ambulance delays over a 12-day period in December.
A spokesman for NHS England said details on the plan "will be published shortly", with a follow-up meeting to be held in two weeks to assess the response of EEAS and other organisations.